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	$87.58	8.317%	$94.864	$94.86	$94.85	$94.90
Purchase #2	$93.41	12.776%	$105.3441	$105.34	$105.35	$105.30
Purchase #3	$227.66	12.424%	$255.9445	$255.94	$255.95	$255.90
Purchase #4	$157.36	11.702%	$175.7743	$175.77	$175.75	$175.80
Purchase #5	$174.46	7.137%	$186.9112	$186.91	$186.90	$186.90
Purchase #6	$28.97	12.608%	$32.6225	$32.62	$32.60	$32.60
Purchase #7	$152.54	8.283%	$165.1749	$165.17	$165.15	$165.20
7 purchase totals =	$921.98		$1,016.6355	$1,016.61	$1,016.55	$1,016.60