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	$33.78	5.304%	$35.5717	$35.57	$35.55	$35.60
Purchase #2	$151.81	13.347%	$172.0721	$172.07	$172.05	$172.10
Purchase #3	$32.48	9.566%	$35.587	$35.59	$35.60	$35.60
Purchase #4	$55.40	5.288%	$58.3296	$58.33	$58.35	$58.30
Purchase #5	$5.88	13.613%	$6.6804	$6.68	$6.70	$6.70
Purchase #6	$108.77	10.432%	$120.1169	$120.12	$120.10	$120.10
Purchase #7	$72.89	13.687%	$82.8665	$82.87	$82.85	$82.90
7 purchase totals =	$461.01		$511.2242	$511.23	$511.20	$511.30