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	$178.38	10.114%	$196.4214	$196.42	$196.40	$196.40
Purchase #2	$118.73	5.198%	$124.9016	$124.90	$124.90	$124.90
Purchase #3	$137.83	10.405%	$152.1712	$152.17	$152.15	$152.20
Purchase #4	$28.36	6.417%	$30.1799	$30.18	$30.20	$30.20
Purchase #5	$22.51	12.172%	$25.2499	$25.25	$25.25	$25.20
Purchase #6	$202.82	10.188%	$223.4833	$223.48	$223.50	$223.50
Purchase #7	$235.67	12.497%	$265.1217	$265.12	$265.10	$265.10
7 purchase totals =	$924.30		$1,017.5290	$1,017.52	$1,017.50	$1,017.50