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	$35.27	6.464%	$37.5499	$37.55	$37.55	$37.50
Purchase #2	$10.79	8.840%	$11.7438	$11.74	$11.75	$11.70
Purchase #3	$148.33	6.255%	$157.608	$157.61	$157.60	$157.60
Purchase #4	$95.99	9.680%	$105.2818	$105.28	$105.30	$105.30
Purchase #5	$78.92	8.416%	$85.5619	$85.56	$85.55	$85.60
Purchase #6	$52.61	10.756%	$58.2687	$58.27	$58.25	$58.30
Purchase #7	$78.78	12.454%	$88.5913	$88.59	$88.60	$88.60
7 purchase totals =	$500.69		$544.6054	$544.60	$544.60	$544.60