Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.44	10.645%	$113.3447	$113.34	$113.35	$113.30
Purchase #2	$118.46	11.453%	$132.0272	$132.03	$132.05	$132.00
Purchase #3	$250.65	3.556%	$259.5631	$259.56	$259.55	$259.60
Purchase #4	$158.85	12.641%	$178.9302	$178.93	$178.95	$178.90
Purchase #5	$144.90	4.836%	$151.9074	$151.91	$151.90	$151.90
Purchase #6	$185.29	13.371%	$210.0651	$210.07	$210.05	$210.10
Purchase #7	$100.57	10.671%	$111.3018	$111.30	$111.30	$111.30
7 purchase totals =	$1,061.16		$1,157.1395	$1,157.14	$1,157.15	$1,157.10