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	$95.59	3.504%	$98.9395	$98.94	$98.95	$98.90
Purchase #2	$36.88	6.239%	$39.1809	$39.18	$39.20	$39.20
Purchase #3	$204.77	8.673%	$222.5297	$222.53	$222.55	$222.50
Purchase #4	$246.29	9.591%	$269.9117	$269.91	$269.90	$269.90
Purchase #5	$164.82	12.618%	$185.617	$185.62	$185.60	$185.60
Purchase #6	$208.43	12.406%	$234.2878	$234.29	$234.30	$234.30
Purchase #7	$190.27	9.383%	$208.123	$208.12	$208.10	$208.10
7 purchase totals =	$1,147.05		$1,258.5896	$1,258.59	$1,258.60	$1,258.50