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	$57.81	7.739%	$62.2839	$62.28	$62.30	$62.30
Purchase #2	$222.51	7.373%	$238.9157	$238.92	$238.90	$238.90
Purchase #3	$61.70	4.757%	$64.6351	$64.64	$64.65	$64.60
Purchase #4	$122.53	10.234%	$135.0697	$135.07	$135.05	$135.10
Purchase #5	$237.58	7.540%	$255.4935	$255.49	$255.50	$255.50
Purchase #6	$82.69	9.692%	$90.7043	$90.70	$90.70	$90.70
Purchase #7	$249.91	13.853%	$284.53	$284.53	$284.55	$284.50
7 purchase totals =	$1,034.73		$1,131.6322	$1,131.63	$1,131.65	$1,131.60