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	$155.90	8.678%	$169.429	$169.43	$169.45	$169.40
Purchase #2	$18.65	13.432%	$21.1551	$21.16	$21.15	$21.20
Purchase #3	$147.82	6.134%	$156.8873	$156.89	$156.90	$156.90
Purchase #4	$106.72	13.793%	$121.4399	$121.44	$121.45	$121.40
Purchase #5	$168.85	12.750%	$190.3784	$190.38	$190.40	$190.40
Purchase #6	$190.85	7.375%	$204.9252	$204.93	$204.95	$204.90
Purchase #7	$58.94	9.853%	$64.7474	$64.75	$64.75	$64.70
7 purchase totals =	$847.73		$928.9623	$928.98	$929.05	$928.90