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	$136.38	3.729%	$141.4656	$141.47	$141.45	$141.50
Purchase #2	$16.59	7.745%	$17.8749	$17.87	$17.85	$17.90
Purchase #3	$105.55	5.391%	$111.2402	$111.24	$111.25	$111.20
Purchase #4	$150.30	3.352%	$155.3381	$155.34	$155.35	$155.30
Purchase #5	$57.39	13.500%	$65.1377	$65.14	$65.15	$65.10
Purchase #6	$191.76	9.371%	$209.7298	$209.73	$209.75	$209.70
Purchase #7	$99.47	11.801%	$111.2085	$111.21	$111.20	$111.20
7 purchase totals =	$757.44		$811.9948	$812.00	$812.00	$811.90