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	$132.25	13.551%	$150.1712	$150.17	$150.15	$150.20
Purchase #2	$114.61	11.835%	$128.1741	$128.17	$128.15	$128.20
Purchase #3	$237.43	6.369%	$252.5519	$252.55	$252.55	$252.60
Purchase #4	$39.27	11.310%	$43.7114	$43.71	$43.70	$43.70
Purchase #5	$76.51	12.795%	$86.2995	$86.30	$86.30	$86.30
Purchase #6	$229.93	11.707%	$256.8479	$256.85	$256.85	$256.80
Purchase #7	$27.37	7.619%	$29.4553	$29.46	$29.45	$29.50
7 purchase totals =	$857.37		$947.2113	$947.21	$947.15	$947.30