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	$192.92	8.598%	$209.5073	$209.51	$209.50	$209.50
Purchase #2	$235.65	12.414%	$264.9036	$264.90	$264.90	$264.90
Purchase #3	$164.83	6.431%	$175.4302	$175.43	$175.45	$175.40
Purchase #4	$34.66	7.688%	$37.3247	$37.32	$37.30	$37.30
Purchase #5	$234.40	6.593%	$249.854	$249.85	$249.85	$249.90
Purchase #6	$153.28	5.470%	$161.6644	$161.66	$161.65	$161.70
Purchase #7	$55.77	10.571%	$61.6654	$61.67	$61.65	$61.70
7 purchase totals =	$1,071.51		$1,160.3496	$1,160.34	$1,160.30	$1,160.40