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	$46.76	6.588%	$49.8405	$49.84	$49.85	$49.80
Purchase #2	$13.28	4.841%	$13.9229	$13.92	$13.90	$13.90
Purchase #3	$91.48	8.704%	$99.4424	$99.44	$99.45	$99.40
Purchase #4	$230.57	4.205%	$240.2655	$240.27	$240.25	$240.30
Purchase #5	$231.48	4.704%	$242.3688	$242.37	$242.35	$242.40
Purchase #6	$234.79	6.676%	$250.4646	$250.46	$250.45	$250.50
Purchase #7	$53.67	3.353%	$55.4696	$55.47	$55.45	$55.50
7 purchase totals =	$902.03		$951.7743	$951.77	$951.70	$951.80