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	$34.44	7.698%	$37.0912	$37.09	$37.10	$37.10
Purchase #2	$209.68	6.576%	$223.4686	$223.47	$223.45	$223.50
Purchase #3	$191.99	4.647%	$200.9118	$200.91	$200.90	$200.90
Purchase #4	$91.36	9.812%	$100.3242	$100.32	$100.30	$100.30
Purchase #5	$155.97	9.610%	$170.9587	$170.96	$170.95	$171.00
Purchase #6	$95.42	10.107%	$105.0641	$105.06	$105.05	$105.10
Purchase #7	$227.65	12.126%	$255.2548	$255.25	$255.25	$255.30
7 purchase totals =	$1,006.51		$1,093.0734	$1,093.06	$1,093.00	$1,093.20