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	$197.62	11.736%	$220.8127	$220.81	$220.80	$220.80
Purchase #2	$125.77	11.303%	$139.9858	$139.99	$140.00	$140.00
Purchase #3	$137.90	12.608%	$155.2864	$155.29	$155.30	$155.30
Purchase #4	$150.38	3.530%	$155.6884	$155.69	$155.70	$155.70
Purchase #5	$77.57	6.245%	$82.4142	$82.41	$82.40	$82.40
Purchase #6	$59.92	9.217%	$65.4428	$65.44	$65.45	$65.40
Purchase #7	$114.76	11.132%	$127.5351	$127.54	$127.55	$127.50
7 purchase totals =	$863.92		$947.1654	$947.17	$947.20	$947.10