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	$100.98	5.304%	$106.336	$106.34	$106.35	$106.30
Purchase #2	$188.78	4.266%	$196.8334	$196.83	$196.85	$196.80
Purchase #3	$26.58	10.217%	$29.2957	$29.30	$29.30	$29.30
Purchase #4	$57.26	7.287%	$61.4325	$61.43	$61.45	$61.40
Purchase #5	$121.48	13.270%	$137.6004	$137.60	$137.60	$137.60
Purchase #6	$185.89	3.143%	$191.7325	$191.73	$191.75	$191.70
Purchase #7	$222.91	8.287%	$241.3826	$241.38	$241.40	$241.40
7 purchase totals =	$903.88		$964.6131	$964.61	$964.70	$964.50