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	$175.93	10.256%	$193.9734	$193.97	$193.95	$194.00
Purchase #2	$59.58	12.350%	$66.9381	$66.94	$66.95	$66.90
Purchase #3	$137.70	9.383%	$150.6204	$150.62	$150.60	$150.60
Purchase #4	$67.72	7.753%	$72.9703	$72.97	$72.95	$73.00
Purchase #5	$134.93	3.430%	$139.5581	$139.56	$139.55	$139.60
Purchase #6	$189.66	10.414%	$209.4112	$209.41	$209.40	$209.40
Purchase #7	$34.51	7.609%	$37.1359	$37.14	$37.15	$37.10
7 purchase totals =	$800.03		$870.6074	$870.61	$870.55	$870.60