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	$90.36	6.757%	$96.4656	$96.47	$96.45	$96.50
Purchase #2	$112.31	5.182%	$118.1299	$118.13	$118.15	$118.10
Purchase #3	$225.83	12.777%	$254.6843	$254.68	$254.70	$254.70
Purchase #4	$142.90	11.181%	$158.8776	$158.88	$158.90	$158.90
Purchase #5	$216.85	12.772%	$244.5461	$244.55	$244.55	$244.50
Purchase #6	$182.39	7.467%	$196.0091	$196.01	$196.00	$196.00
Purchase #7	$145.50	6.540%	$155.0157	$155.02	$155.00	$155.00
7 purchase totals =	$1,116.14		$1,223.7283	$1,223.74	$1,223.75	$1,223.70