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	$65.37	3.128%	$67.4148	$67.41	$67.40	$67.40
Purchase #2	$208.97	5.817%	$221.1258	$221.13	$221.15	$221.10
Purchase #3	$166.68	5.362%	$175.6174	$175.62	$175.60	$175.60
Purchase #4	$184.31	6.632%	$196.5334	$196.53	$196.55	$196.50
Purchase #5	$95.77	6.562%	$102.0544	$102.05	$102.05	$102.10
Purchase #6	$77.83	12.803%	$87.7946	$87.79	$87.80	$87.80
Purchase #7	$125.32	5.716%	$132.4833	$132.48	$132.50	$132.50
7 purchase totals =	$924.25		$983.0237	$983.01	$983.05	$983.00