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	$129.96	10.365%	$143.4304	$143.43	$143.45	$143.40
Purchase #2	$175.38	5.307%	$184.6874	$184.69	$184.70	$184.70
Purchase #3	$64.79	11.398%	$72.1748	$72.17	$72.15	$72.20
Purchase #4	$102.71	5.854%	$108.7226	$108.72	$108.70	$108.70
Purchase #5	$143.41	4.227%	$149.4719	$149.47	$149.45	$149.50
Purchase #6	$152.61	8.835%	$166.0931	$166.09	$166.10	$166.10
Purchase #7	$49.38	7.113%	$52.8924	$52.89	$52.90	$52.90
7 purchase totals =	$818.24		$877.4726	$877.46	$877.45	$877.50