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	$223.78	8.854%	$243.5935	$243.59	$243.60	$243.60
Purchase #2	$223.25	7.121%	$239.1476	$239.15	$239.15	$239.10
Purchase #3	$55.71	7.361%	$59.8108	$59.81	$59.80	$59.80
Purchase #4	$235.38	8.161%	$254.5894	$254.59	$254.60	$254.60
Purchase #5	$78.47	10.741%	$86.8985	$86.90	$86.90	$86.90
Purchase #6	$199.41	5.283%	$209.9448	$209.94	$209.95	$209.90
Purchase #7	$73.73	10.666%	$81.594	$81.59	$81.60	$81.60
7 purchase totals =	$1,089.73		$1,175.5786	$1,175.57	$1,175.60	$1,175.50