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	$141.74	7.608%	$152.5236	$152.52	$152.50	$152.50
Purchase #2	$103.47	9.804%	$113.6142	$113.61	$113.60	$113.60
Purchase #3	$47.54	6.827%	$50.7856	$50.79	$50.80	$50.80
Purchase #4	$91.34	9.163%	$99.7095	$99.71	$99.70	$99.70
Purchase #5	$141.99	9.406%	$155.3456	$155.35	$155.35	$155.30
Purchase #6	$147.84	3.680%	$153.2805	$153.28	$153.30	$153.30
Purchase #7	$98.25	12.867%	$110.8918	$110.89	$110.90	$110.90
7 purchase totals =	$772.17		$836.1508	$836.15	$836.15	$836.10