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	$244.64	7.607%	$263.2498	$263.25	$263.25	$263.20
Purchase #2	$71.46	10.134%	$78.7018	$78.70	$78.70	$78.70
Purchase #3	$99.93	11.352%	$111.2741	$111.27	$111.25	$111.30
Purchase #4	$208.84	6.842%	$223.1288	$223.13	$223.15	$223.10
Purchase #5	$220.25	7.653%	$237.1057	$237.11	$237.10	$237.10
Purchase #6	$60.56	3.218%	$62.5088	$62.51	$62.50	$62.50
Purchase #7	$111.93	5.573%	$118.1679	$118.17	$118.15	$118.20
7 purchase totals =	$1,017.61		$1,094.1369	$1,094.14	$1,094.10	$1,094.10