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	$62.62	4.614%	$65.5093	$65.51	$65.50	$65.50
Purchase #2	$74.59	5.267%	$78.5187	$78.52	$78.50	$78.50
Purchase #3	$15.92	3.169%	$16.4245	$16.42	$16.40	$16.40
Purchase #4	$170.51	12.410%	$191.6703	$191.67	$191.65	$191.70
Purchase #5	$114.46	8.802%	$124.5348	$124.53	$124.55	$124.50
Purchase #6	$75.66	3.165%	$78.0546	$78.05	$78.05	$78.10
Purchase #7	$241.69	8.620%	$262.5237	$262.52	$262.50	$262.50
7 purchase totals =	$755.45		$817.2359	$817.22	$817.15	$817.20