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	$184.70	13.414%	$209.4757	$209.48	$209.50	$209.50
Purchase #2	$196.41	6.580%	$209.3338	$209.33	$209.35	$209.30
Purchase #3	$133.99	12.833%	$151.1849	$151.18	$151.20	$151.20
Purchase #4	$60.40	12.343%	$67.8552	$67.86	$67.85	$67.90
Purchase #5	$85.52	7.431%	$91.875	$91.88	$91.90	$91.90
Purchase #6	$244.57	10.225%	$269.5773	$269.58	$269.60	$269.60
Purchase #7	$236.81	8.688%	$257.3841	$257.38	$257.40	$257.40
7 purchase totals =	$1,142.40		$1,256.6860	$1,256.69	$1,256.80	$1,256.80