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	$164.81	8.111%	$178.1777	$178.18	$178.20	$178.20
Purchase #2	$67.96	7.604%	$73.1277	$73.13	$73.15	$73.10
Purchase #3	$116.61	6.796%	$124.5348	$124.53	$124.55	$124.50
Purchase #4	$233.33	13.294%	$264.3489	$264.35	$264.35	$264.30
Purchase #5	$157.57	5.245%	$165.8345	$165.83	$165.85	$165.80
Purchase #6	$119.58	7.603%	$128.6717	$128.67	$128.65	$128.70
Purchase #7	$141.34	13.299%	$160.1368	$160.14	$160.15	$160.10
7 purchase totals =	$1,001.20		$1,094.8321	$1,094.83	$1,094.90	$1,094.70