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	$178.63	3.333%	$184.5837	$184.58	$184.60	$184.60
Purchase #2	$227.77	5.522%	$240.3475	$240.35	$240.35	$240.30
Purchase #3	$145.96	4.231%	$152.1356	$152.14	$152.15	$152.10
Purchase #4	$183.78	8.208%	$198.8647	$198.86	$198.85	$198.90
Purchase #5	$20.43	6.554%	$21.769	$21.77	$21.75	$21.80
Purchase #6	$90.45	5.630%	$95.5423	$95.54	$95.55	$95.50
Purchase #7	$28.82	12.582%	$32.4461	$32.45	$32.45	$32.40
7 purchase totals =	$875.84		$925.6889	$925.69	$925.70	$925.60