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	$100.92	12.320%	$113.3533	$113.35	$113.35	$113.40
Purchase #2	$179.37	7.126%	$192.1519	$192.15	$192.15	$192.20
Purchase #3	$196.47	13.459%	$222.9129	$222.91	$222.90	$222.90
Purchase #4	$118.51	10.277%	$130.6893	$130.69	$130.70	$130.70
Purchase #5	$130.98	3.854%	$136.028	$136.03	$136.05	$136.00
Purchase #6	$165.36	10.591%	$182.8733	$182.87	$182.85	$182.90
Purchase #7	$66.90	6.534%	$71.2712	$71.27	$71.25	$71.30
7 purchase totals =	$958.51		$1,049.2799	$1,049.27	$1,049.25	$1,049.40