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	$67.70	8.449%	$73.42	$73.42	$73.40	$73.40
Purchase #2	$43.42	11.533%	$48.4276	$48.43	$48.45	$48.40
Purchase #3	$148.27	11.166%	$164.8258	$164.83	$164.85	$164.80
Purchase #4	$155.84	11.162%	$173.2349	$173.23	$173.25	$173.20
Purchase #5	$223.97	8.706%	$243.4688	$243.47	$243.45	$243.50
Purchase #6	$135.47	9.652%	$148.5456	$148.55	$148.55	$148.50
Purchase #7	$241.31	9.470%	$264.1621	$264.16	$264.15	$264.20
7 purchase totals =	$1,015.98		$1,116.0848	$1,116.09	$1,116.10	$1,116.00