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	$71.78	3.149%	$74.0404	$74.04	$74.05	$74.00
Purchase #2	$100.70	9.199%	$109.9634	$109.96	$109.95	$110.00
Purchase #3	$216.94	10.478%	$239.671	$239.67	$239.65	$239.70
Purchase #4	$242.72	5.190%	$255.3172	$255.32	$255.30	$255.30
Purchase #5	$124.35	10.306%	$137.1655	$137.17	$137.15	$137.20
Purchase #6	$44.59	13.529%	$50.6226	$50.62	$50.60	$50.60
Purchase #7	$175.69	11.858%	$196.5233	$196.52	$196.50	$196.50
7 purchase totals =	$976.77		$1,063.3034	$1,063.30	$1,063.20	$1,063.30