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	$48.66	8.792%	$52.9382	$52.94	$52.95	$52.90
Purchase #2	$156.34	9.560%	$171.2861	$171.29	$171.30	$171.30
Purchase #3	$14.40	13.401%	$16.3297	$16.33	$16.35	$16.30
Purchase #4	$38.61	12.436%	$43.4115	$43.41	$43.40	$43.40
Purchase #5	$140.69	13.443%	$159.603	$159.60	$159.60	$159.60
Purchase #6	$85.54	4.656%	$89.5227	$89.52	$89.50	$89.50
Purchase #7	$67.57	10.576%	$74.7162	$74.72	$74.70	$74.70
7 purchase totals =	$551.81		$607.8074	$607.81	$607.80	$607.70