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	$90.35	3.454%	$93.4707	$93.47	$93.45	$93.50
Purchase #2	$12.98	4.692%	$13.589	$13.59	$13.60	$13.60
Purchase #3	$208.54	6.685%	$222.4809	$222.48	$222.50	$222.50
Purchase #4	$120.41	3.344%	$124.4365	$124.44	$124.45	$124.40
Purchase #5	$95.69	5.221%	$100.686	$100.69	$100.70	$100.70
Purchase #6	$124.54	12.692%	$140.3466	$140.35	$140.35	$140.30
Purchase #7	$93.88	7.436%	$100.8609	$100.86	$100.85	$100.90
7 purchase totals =	$746.39		$795.8706	$795.88	$795.90	$795.90