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	$72.98	10.393%	$80.5648	$80.56	$80.55	$80.60
Purchase #2	$30.79	9.108%	$33.5944	$33.59	$33.60	$33.60
Purchase #3	$140.80	8.281%	$152.4596	$152.46	$152.45	$152.50
Purchase #4	$49.53	6.549%	$52.7737	$52.77	$52.75	$52.80
Purchase #5	$35.71	12.862%	$40.303	$40.30	$40.30	$40.30
Purchase #6	$85.89	8.537%	$93.2224	$93.22	$93.20	$93.20
Purchase #7	$27.61	11.761%	$30.8572	$30.86	$30.85	$30.90
7 purchase totals =	$443.31		$483.7751	$483.76	$483.70	$483.90