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	$178.35	10.264%	$196.6558	$196.66	$196.65	$196.70
Purchase #2	$234.27	5.829%	$247.9256	$247.93	$247.95	$247.90
Purchase #3	$206.39	10.184%	$227.4088	$227.41	$227.40	$227.40
Purchase #4	$146.71	13.405%	$166.3765	$166.38	$166.40	$166.40
Purchase #5	$244.82	12.411%	$275.2046	$275.20	$275.20	$275.20
Purchase #6	$64.61	13.609%	$73.4028	$73.40	$73.40	$73.40
Purchase #7	$29.73	9.800%	$32.6435	$32.64	$32.65	$32.60
7 purchase totals =	$1,104.88		$1,219.6176	$1,219.62	$1,219.65	$1,219.60