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	$59.80	3.216%	$61.7232	$61.72	$61.70	$61.70
Purchase #2	$215.76	7.200%	$231.2947	$231.29	$231.30	$231.30
Purchase #3	$164.68	9.831%	$180.8697	$180.87	$180.85	$180.90
Purchase #4	$247.90	4.295%	$258.5473	$258.55	$258.55	$258.50
Purchase #5	$19.48	13.333%	$22.0773	$22.08	$22.10	$22.10
Purchase #6	$159.45	12.462%	$179.3207	$179.32	$179.30	$179.30
Purchase #7	$186.78	12.244%	$209.6493	$209.65	$209.65	$209.60
7 purchase totals =	$1,053.85		$1,143.4822	$1,143.48	$1,143.45	$1,143.40