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	$116.84	13.173%	$132.2313	$132.23	$132.25	$132.20
Purchase #2	$104.82	4.123%	$109.1417	$109.14	$109.15	$109.10
Purchase #3	$199.89	9.446%	$218.7716	$218.77	$218.75	$218.80
Purchase #4	$234.55	13.389%	$265.9539	$265.95	$265.95	$266.00
Purchase #5	$63.75	11.634%	$71.1667	$71.17	$71.15	$71.20
Purchase #6	$89.29	8.306%	$96.7064	$96.71	$96.70	$96.70
Purchase #7	$166.45	11.216%	$185.119	$185.12	$185.10	$185.10
7 purchase totals =	$975.59		$1,079.0906	$1,079.09	$1,079.05	$1,079.10