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	$227.72	12.742%	$256.7361	$256.74	$256.75	$256.70
Purchase #2	$84.97	7.555%	$91.3895	$91.39	$91.40	$91.40
Purchase #3	$241.31	5.873%	$255.4821	$255.48	$255.50	$255.50
Purchase #4	$99.31	3.136%	$102.4244	$102.42	$102.40	$102.40
Purchase #5	$82.34	11.130%	$91.5044	$91.50	$91.50	$91.50
Purchase #6	$165.71	11.106%	$184.1138	$184.11	$184.10	$184.10
Purchase #7	$57.85	9.804%	$63.5216	$63.52	$63.50	$63.50
7 purchase totals =	$959.21		$1,045.1719	$1,045.16	$1,045.15	$1,045.10