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	$92.51	10.610%	$102.3253	$102.33	$102.35	$102.30
Purchase #2	$238.76	4.527%	$249.5687	$249.57	$249.55	$249.60
Purchase #3	$151.32	10.304%	$166.912	$166.91	$166.90	$166.90
Purchase #4	$222.42	11.852%	$248.7812	$248.78	$248.80	$248.80
Purchase #5	$64.96	9.221%	$70.95	$70.95	$70.95	$71.00
Purchase #6	$205.53	9.330%	$224.7059	$224.71	$224.70	$224.70
Purchase #7	$34.72	7.500%	$37.324	$37.32	$37.30	$37.30
7 purchase totals =	$1,010.22		$1,100.5671	$1,100.57	$1,100.55	$1,100.60