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	$185.50	4.245%	$193.3745	$193.37	$193.35	$193.40
Purchase #2	$203.58	11.817%	$227.637	$227.64	$227.65	$227.60
Purchase #3	$39.94	5.794%	$42.2541	$42.25	$42.25	$42.30
Purchase #4	$38.88	8.334%	$42.1203	$42.12	$42.10	$42.10
Purchase #5	$25.46	7.580%	$27.3899	$27.39	$27.40	$27.40
Purchase #6	$43.56	3.557%	$45.1094	$45.11	$45.10	$45.10
Purchase #7	$165.67	7.138%	$177.4955	$177.50	$177.50	$177.50
7 purchase totals =	$702.59		$755.3807	$755.38	$755.35	$755.40