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	$155.89	6.623%	$166.2146	$166.21	$166.20	$166.20
Purchase #2	$9.38	6.823%	$10.02	$10.02	$10.00	$10.00
Purchase #3	$223.58	6.426%	$237.9473	$237.95	$237.95	$237.90
Purchase #4	$97.63	7.437%	$104.8907	$104.89	$104.90	$104.90
Purchase #5	$75.59	13.647%	$85.9058	$85.91	$85.90	$85.90
Purchase #6	$237.38	13.377%	$269.1343	$269.13	$269.15	$269.10
Purchase #7	$131.36	12.839%	$148.2253	$148.23	$148.25	$148.20
7 purchase totals =	$930.81		$1,022.3380	$1,022.34	$1,022.35	$1,022.20