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	$60.41	7.729%	$65.0791	$65.08	$65.10	$65.10
Purchase #2	$13.63	6.437%	$14.5074	$14.51	$14.50	$14.50
Purchase #3	$136.92	11.198%	$152.2523	$152.25	$152.25	$152.30
Purchase #4	$104.98	13.814%	$119.4819	$119.48	$119.50	$119.50
Purchase #5	$10.98	11.808%	$12.2765	$12.28	$12.30	$12.30
Purchase #6	$156.46	5.820%	$165.566	$165.57	$165.55	$165.60
Purchase #7	$76.92	8.414%	$83.392	$83.39	$83.40	$83.40
7 purchase totals =	$560.30		$612.5552	$612.56	$612.60	$612.70