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	$161.59	3.179%	$166.7269	$166.73	$166.75	$166.70
Purchase #2	$20.65	7.709%	$22.2419	$22.24	$22.25	$22.20
Purchase #3	$76.61	3.804%	$79.5242	$79.52	$79.50	$79.50
Purchase #4	$152.25	8.649%	$165.4181	$165.42	$165.40	$165.40
Purchase #5	$223.32	13.215%	$252.8317	$252.83	$252.85	$252.80
Purchase #6	$159.76	3.359%	$165.1263	$165.13	$165.15	$165.10
Purchase #7	$85.74	5.573%	$90.5183	$90.52	$90.50	$90.50
7 purchase totals =	$879.92		$942.3874	$942.39	$942.40	$942.20