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	$57.51	3.298%	$59.4067	$59.41	$59.40	$59.40
Purchase #2	$173.29	4.394%	$180.9044	$180.90	$180.90	$180.90
Purchase #3	$19.51	4.797%	$20.4459	$20.45	$20.45	$20.40
Purchase #4	$12.26	12.680%	$13.8146	$13.81	$13.80	$13.80
Purchase #5	$161.36	9.500%	$176.6892	$176.69	$176.70	$176.70
Purchase #6	$156.86	5.604%	$165.6504	$165.65	$165.65	$165.70
Purchase #7	$145.82	4.784%	$152.796	$152.80	$152.80	$152.80
7 purchase totals =	$726.61		$769.7072	$769.71	$769.70	$769.70