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	$99.31	4.562%	$103.8405	$103.84	$103.85	$103.80
Purchase #2	$65.68	4.833%	$68.8543	$68.85	$68.85	$68.90
Purchase #3	$9.95	5.443%	$10.4916	$10.49	$10.50	$10.50
Purchase #4	$160.50	6.486%	$170.91	$170.91	$170.90	$170.90
Purchase #5	$32.35	9.759%	$35.507	$35.51	$35.50	$35.50
Purchase #6	$61.86	9.187%	$67.5431	$67.54	$67.55	$67.50
Purchase #7	$55.55	13.699%	$63.1598	$63.16	$63.15	$63.20
7 purchase totals =	$485.20		$520.3063	$520.30	$520.30	$520.30