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	$167.65	7.859%	$180.8256	$180.83	$180.85	$180.80
Purchase #2	$151.36	13.447%	$171.7134	$171.71	$171.70	$171.70
Purchase #3	$67.34	7.203%	$72.1905	$72.19	$72.20	$72.20
Purchase #4	$72.49	11.593%	$80.8938	$80.89	$80.90	$80.90
Purchase #5	$232.31	10.258%	$256.1404	$256.14	$256.15	$256.10
Purchase #6	$101.75	8.496%	$110.3947	$110.39	$110.40	$110.40
Purchase #7	$59.49	4.499%	$62.1665	$62.17	$62.15	$62.20
7 purchase totals =	$852.39		$934.3249	$934.32	$934.35	$934.30