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	$235.77	12.504%	$265.2507	$265.25	$265.25	$265.30
Purchase #2	$172.50	7.452%	$185.3547	$185.35	$185.35	$185.40
Purchase #3	$93.99	11.125%	$104.4464	$104.45	$104.45	$104.40
Purchase #4	$97.96	6.443%	$104.2716	$104.27	$104.25	$104.30
Purchase #5	$106.51	4.338%	$111.1304	$111.13	$111.15	$111.10
Purchase #6	$170.34	6.206%	$180.9113	$180.91	$180.90	$180.90
Purchase #7	$190.89	11.860%	$213.5296	$213.53	$213.55	$213.50
7 purchase totals =	$1,067.96		$1,164.8947	$1,164.89	$1,164.90	$1,164.90