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	$77.56	6.662%	$82.727	$82.73	$82.75	$82.70
Purchase #2	$13.31	13.676%	$15.1303	$15.13	$15.15	$15.10
Purchase #3	$111.34	7.314%	$119.4834	$119.48	$119.50	$119.50
Purchase #4	$121.60	6.873%	$129.9576	$129.96	$129.95	$130.00
Purchase #5	$90.54	5.526%	$95.5432	$95.54	$95.55	$95.50
Purchase #6	$37.61	9.303%	$41.1089	$41.11	$41.10	$41.10
Purchase #7	$182.72	3.289%	$188.7297	$188.73	$188.75	$188.70
7 purchase totals =	$634.68		$672.6801	$672.68	$672.75	$672.60