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	$144.77	4.523%	$151.3179	$151.32	$151.30	$151.30
Purchase #2	$32.90	12.347%	$36.9622	$36.96	$36.95	$37.00
Purchase #3	$189.75	5.856%	$200.8618	$200.86	$200.85	$200.90
Purchase #4	$60.56	9.506%	$66.3168	$66.32	$66.30	$66.30
Purchase #5	$243.25	13.576%	$276.2736	$276.27	$276.25	$276.30
Purchase #6	$116.71	3.366%	$120.6385	$120.64	$120.65	$120.60
Purchase #7	$89.38	6.565%	$95.2478	$95.25	$95.25	$95.20
7 purchase totals =	$877.32		$947.6186	$947.62	$947.55	$947.60