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	$32.59	7.802%	$35.1327	$35.13	$35.15	$35.10
Purchase #2	$98.28	6.555%	$104.7223	$104.72	$104.70	$104.70
Purchase #3	$104.78	11.211%	$116.5269	$116.53	$116.55	$116.50
Purchase #4	$191.90	12.121%	$215.1602	$215.16	$215.15	$215.20
Purchase #5	$177.93	12.711%	$200.5467	$200.55	$200.55	$200.50
Purchase #6	$127.89	4.454%	$133.5862	$133.59	$133.60	$133.60
Purchase #7	$173.29	10.258%	$191.0661	$191.07	$191.05	$191.10
7 purchase totals =	$906.66		$996.7411	$996.75	$996.75	$996.70