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	$151.46	11.771%	$169.2884	$169.29	$169.30	$169.30
Purchase #2	$42.27	7.684%	$45.518	$45.52	$45.50	$45.50
Purchase #3	$219.93	4.790%	$230.4646	$230.46	$230.45	$230.50
Purchase #4	$155.47	12.567%	$175.0079	$175.01	$175.00	$175.00
Purchase #5	$141.57	7.378%	$152.015	$152.02	$152.00	$152.00
Purchase #6	$136.96	12.221%	$153.6979	$153.70	$153.70	$153.70
Purchase #7	$129.32	13.301%	$146.5209	$146.52	$146.50	$146.50
7 purchase totals =	$976.98		$1,072.5127	$1,072.52	$1,072.45	$1,072.50