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	$64.86	11.201%	$72.125	$72.13	$72.15	$72.10
Purchase #2	$135.73	11.373%	$151.1666	$151.17	$151.15	$151.20
Purchase #3	$112.57	6.278%	$119.6371	$119.64	$119.65	$119.60
Purchase #4	$48.82	3.121%	$50.3437	$50.34	$50.35	$50.30
Purchase #5	$131.78	6.792%	$140.7305	$140.73	$140.75	$140.70
Purchase #6	$43.96	13.651%	$49.961	$49.96	$49.95	$50.00
Purchase #7	$215.82	10.432%	$238.3343	$238.33	$238.35	$238.30
7 purchase totals =	$753.54		$822.2982	$822.30	$822.35	$822.20