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	$246.65	9.412%	$269.8647	$269.86	$269.85	$269.90
Purchase #2	$177.97	4.625%	$186.2011	$186.20	$186.20	$186.20
Purchase #3	$219.39	4.792%	$229.9032	$229.90	$229.90	$229.90
Purchase #4	$133.89	9.118%	$146.0981	$146.10	$146.10	$146.10
Purchase #5	$189.83	9.781%	$208.3973	$208.40	$208.40	$208.40
Purchase #6	$43.83	4.238%	$45.6875	$45.69	$45.70	$45.70
Purchase #7	$215.75	12.863%	$243.5019	$243.50	$243.50	$243.50
7 purchase totals =	$1,227.31		$1,329.6538	$1,329.65	$1,329.65	$1,329.70