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	$116.98	9.775%	$128.4148	$128.41	$128.40	$128.40
Purchase #2	$39.29	11.373%	$43.7585	$43.76	$43.75	$43.80
Purchase #3	$177.91	7.201%	$190.7213	$190.72	$190.70	$190.70
Purchase #4	$236.40	8.426%	$256.3191	$256.32	$256.30	$256.30
Purchase #5	$64.43	11.873%	$72.0798	$72.08	$72.10	$72.10
Purchase #6	$176.55	5.725%	$186.6575	$186.66	$186.65	$186.70
Purchase #7	$42.33	6.640%	$45.1407	$45.14	$45.15	$45.10
7 purchase totals =	$853.89		$923.0917	$923.09	$923.05	$923.10