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	$211.78	3.471%	$219.1309	$219.13	$219.15	$219.10
Purchase #2	$246.69	11.721%	$275.6045	$275.60	$275.60	$275.60
Purchase #3	$61.76	10.861%	$68.4678	$68.47	$68.45	$68.50
Purchase #4	$138.32	6.365%	$147.1241	$147.12	$147.10	$147.10
Purchase #5	$37.64	8.459%	$40.824	$40.82	$40.80	$40.80
Purchase #6	$102.88	10.532%	$113.7153	$113.72	$113.70	$113.70
Purchase #7	$59.41	12.594%	$66.8921	$66.89	$66.90	$66.90
7 purchase totals =	$858.48		$931.7587	$931.75	$931.70	$931.70