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	$174.87	6.231%	$185.7661	$185.77	$185.75	$185.80
Purchase #2	$38.59	5.368%	$40.6615	$40.66	$40.65	$40.70
Purchase #3	$199.53	7.508%	$214.5107	$214.51	$214.50	$214.50
Purchase #4	$227.48	10.137%	$250.5396	$250.54	$250.55	$250.50
Purchase #5	$247.91	9.230%	$270.7921	$270.79	$270.80	$270.80
Purchase #6	$40.47	11.763%	$45.2305	$45.23	$45.25	$45.20
Purchase #7	$179.32	13.461%	$203.4583	$203.46	$203.45	$203.50
7 purchase totals =	$1,108.17		$1,210.9588	$1,210.96	$1,210.95	$1,211.00