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	$59.83	7.779%	$64.4842	$64.48	$64.50	$64.50
Purchase #2	$130.58	7.871%	$140.858	$140.86	$140.85	$140.90
Purchase #3	$205.73	8.557%	$223.3343	$223.33	$223.35	$223.30
Purchase #4	$15.78	6.773%	$16.8488	$16.85	$16.85	$16.80
Purchase #5	$16.43	12.850%	$18.5413	$18.54	$18.55	$18.50
Purchase #6	$196.56	4.386%	$205.1811	$205.18	$205.20	$205.20
Purchase #7	$153.63	7.528%	$165.1953	$165.20	$165.20	$165.20
7 purchase totals =	$778.54		$834.4430	$834.44	$834.50	$834.40