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	$231.38	10.186%	$254.9484	$254.95	$254.95	$254.90
Purchase #2	$233.58	12.290%	$262.287	$262.29	$262.30	$262.30
Purchase #3	$115.25	3.719%	$119.5361	$119.54	$119.55	$119.50
Purchase #4	$133.61	7.272%	$143.3261	$143.33	$143.35	$143.30
Purchase #5	$13.82	9.560%	$15.1412	$15.14	$15.15	$15.10
Purchase #6	$223.30	8.120%	$241.432	$241.43	$241.45	$241.40
Purchase #7	$24.27	3.736%	$25.1767	$25.18	$25.20	$25.20
7 purchase totals =	$975.21		$1,061.8475	$1,061.86	$1,061.95	$1,061.70