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	$194.33	7.519%	$208.9417	$208.94	$208.95	$208.90
Purchase #2	$95.67	9.776%	$105.0227	$105.02	$105.00	$105.00
Purchase #3	$50.57	12.165%	$56.7218	$56.72	$56.70	$56.70
Purchase #4	$162.41	5.607%	$171.5163	$171.52	$171.50	$171.50
Purchase #5	$53.63	5.144%	$56.3887	$56.39	$56.40	$56.40
Purchase #6	$84.40	3.532%	$87.381	$87.38	$87.40	$87.40
Purchase #7	$83.78	8.481%	$90.8854	$90.89	$90.90	$90.90
7 purchase totals =	$724.79		$776.8576	$776.86	$776.85	$776.80