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	$120.85	11.413%	$134.6426	$134.64	$134.65	$134.60
Purchase #2	$196.52	13.538%	$223.1249	$223.12	$223.10	$223.10
Purchase #3	$204.99	7.279%	$219.9112	$219.91	$219.90	$219.90
Purchase #4	$209.70	10.236%	$231.1649	$231.16	$231.15	$231.20
Purchase #5	$50.28	10.389%	$55.5036	$55.50	$55.50	$55.50
Purchase #6	$67.96	5.301%	$71.5626	$71.56	$71.55	$71.60
Purchase #7	$65.72	10.813%	$72.8263	$72.83	$72.85	$72.80
7 purchase totals =	$916.02		$1,008.7361	$1,008.72	$1,008.70	$1,008.70