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	$33.43	9.776%	$36.6981	$36.70	$36.70	$36.70
Purchase #2	$49.31	7.182%	$52.8514	$52.85	$52.85	$52.90
Purchase #3	$158.59	12.633%	$178.6247	$178.62	$178.60	$178.60
Purchase #4	$238.37	7.472%	$256.181	$256.18	$256.20	$256.20
Purchase #5	$147.25	7.282%	$157.9727	$157.97	$157.95	$158.00
Purchase #6	$150.59	13.648%	$171.1425	$171.14	$171.15	$171.10
Purchase #7	$237.89	11.266%	$264.6907	$264.69	$264.70	$264.70
7 purchase totals =	$1,015.43		$1,118.1611	$1,118.15	$1,118.15	$1,118.20