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	$147.64	8.546%	$160.2573	$160.26	$160.25	$160.30
Purchase #2	$248.91	10.813%	$275.8246	$275.82	$275.80	$275.80
Purchase #3	$38.74	10.373%	$42.7585	$42.76	$42.75	$42.80
Purchase #4	$32.35	3.487%	$33.478	$33.48	$33.50	$33.50
Purchase #5	$46.78	3.492%	$48.4136	$48.41	$48.40	$48.40
Purchase #6	$35.47	12.367%	$39.8566	$39.86	$39.85	$39.90
Purchase #7	$147.49	8.165%	$159.5326	$159.53	$159.55	$159.50
7 purchase totals =	$697.38		$760.1212	$760.12	$760.10	$760.20