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	$112.52	11.702%	$125.6871	$125.69	$125.70	$125.70
Purchase #2	$76.38	7.407%	$82.0375	$82.04	$82.05	$82.00
Purchase #3	$148.28	10.630%	$164.0422	$164.04	$164.05	$164.00
Purchase #4	$248.43	8.483%	$269.5043	$269.50	$269.50	$269.50
Purchase #5	$221.33	5.333%	$233.1335	$233.13	$233.15	$233.10
Purchase #6	$133.68	9.629%	$146.552	$146.55	$146.55	$146.60
Purchase #7	$110.27	7.141%	$118.1444	$118.14	$118.15	$118.10
7 purchase totals =	$1,050.89		$1,139.1010	$1,139.09	$1,139.15	$1,139.00