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	$43.41	12.209%	$48.7099	$48.71	$48.70	$48.70
Purchase #2	$58.53	6.123%	$62.1138	$62.11	$62.10	$62.10
Purchase #3	$45.96	12.779%	$51.8332	$51.83	$51.85	$51.80
Purchase #4	$44.65	4.179%	$46.5159	$46.52	$46.50	$46.50
Purchase #5	$174.92	3.417%	$180.897	$180.90	$180.90	$180.90
Purchase #6	$77.93	9.512%	$85.3427	$85.34	$85.35	$85.30
Purchase #7	$126.79	11.362%	$141.1959	$141.20	$141.20	$141.20
7 purchase totals =	$572.19		$616.6084	$616.61	$616.60	$616.50