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	$125.83	13.293%	$142.5566	$142.56	$142.55	$142.60
Purchase #2	$178.61	11.836%	$199.7503	$199.75	$199.75	$199.80
Purchase #3	$106.69	4.168%	$111.1368	$111.14	$111.15	$111.10
Purchase #4	$116.57	13.303%	$132.0773	$132.08	$132.10	$132.10
Purchase #5	$118.34	6.399%	$125.9126	$125.91	$125.90	$125.90
Purchase #6	$93.76	9.486%	$102.6541	$102.65	$102.65	$102.70
Purchase #7	$169.72	11.402%	$189.0715	$189.07	$189.05	$189.10
7 purchase totals =	$909.52		$1,003.1592	$1,003.16	$1,003.15	$1,003.30