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	$169.40	13.109%	$191.6066	$191.61	$191.60	$191.60
Purchase #2	$118.89	4.854%	$124.6609	$124.66	$124.65	$124.70
Purchase #3	$147.64	12.840%	$166.597	$166.60	$166.60	$166.60
Purchase #4	$165.73	7.414%	$178.0172	$178.02	$178.00	$178.00
Purchase #5	$97.31	8.252%	$105.34	$105.34	$105.35	$105.30
Purchase #6	$88.51	4.845%	$92.7983	$92.80	$92.80	$92.80
Purchase #7	$14.51	6.599%	$15.4675	$15.47	$15.45	$15.50
7 purchase totals =	$801.99		$874.4875	$874.50	$874.45	$874.50