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	$245.25	5.562%	$258.8908	$258.89	$258.90	$258.90
Purchase #2	$34.97	13.796%	$39.7945	$39.79	$39.80	$39.80
Purchase #3	$40.27	12.322%	$45.2321	$45.23	$45.25	$45.20
Purchase #4	$160.56	7.704%	$172.9295	$172.93	$172.95	$172.90
Purchase #5	$224.26	11.197%	$249.3704	$249.37	$249.35	$249.40
Purchase #6	$120.81	11.315%	$134.4797	$134.48	$134.50	$134.50
Purchase #7	$238.38	3.301%	$246.2489	$246.25	$246.25	$246.20
7 purchase totals =	$1,064.50		$1,146.9459	$1,146.94	$1,147.00	$1,146.90