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	$10.70	4.123%	$11.1412	$11.14	$11.15	$11.10
Purchase #2	$22.93	5.226%	$24.1283	$24.13	$24.15	$24.10
Purchase #3	$10.34	7.536%	$11.1192	$11.12	$11.10	$11.10
Purchase #4	$67.36	8.779%	$73.2735	$73.27	$73.25	$73.30
Purchase #5	$199.81	12.338%	$224.4626	$224.46	$224.45	$224.50
Purchase #6	$78.60	8.502%	$85.2826	$85.28	$85.30	$85.30
Purchase #7	$57.92	3.282%	$59.8209	$59.82	$59.80	$59.80
7 purchase totals =	$447.66		$489.2283	$489.22	$489.20	$489.20