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	$67.28	5.739%	$71.1412	$71.14	$71.15	$71.10
Purchase #2	$19.35	11.299%	$21.5364	$21.54	$21.55	$21.50
Purchase #3	$238.43	13.591%	$270.835	$270.84	$270.85	$270.80
Purchase #4	$216.90	9.160%	$236.768	$236.77	$236.75	$236.80
Purchase #5	$157.85	5.760%	$166.9422	$166.94	$166.95	$166.90
Purchase #6	$193.72	11.790%	$216.5596	$216.56	$216.55	$216.60
Purchase #7	$130.28	13.738%	$148.1779	$148.18	$148.20	$148.20
7 purchase totals =	$1,023.81		$1,131.9603	$1,131.97	$1,132.00	$1,131.90