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	$37.62	9.507%	$41.1965	$41.20	$41.20	$41.20
Purchase #2	$135.50	3.651%	$140.4471	$140.45	$140.45	$140.40
Purchase #3	$155.54	12.109%	$174.3743	$174.37	$174.35	$174.40
Purchase #4	$96.63	4.133%	$100.6237	$100.62	$100.60	$100.60
Purchase #5	$96.69	13.624%	$109.863	$109.86	$109.85	$109.90
Purchase #6	$182.78	9.252%	$199.6908	$199.69	$199.70	$199.70
Purchase #7	$124.70	13.315%	$141.3038	$141.30	$141.30	$141.30
7 purchase totals =	$829.46		$907.4992	$907.49	$907.45	$907.50