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	$141.64	6.873%	$151.3749	$151.37	$151.35	$151.40
Purchase #2	$217.46	13.510%	$246.8388	$246.84	$246.85	$246.80
Purchase #3	$60.90	13.307%	$69.004	$69.00	$69.00	$69.00
Purchase #4	$60.62	11.524%	$67.6058	$67.61	$67.60	$67.60
Purchase #5	$62.96	7.606%	$67.7487	$67.75	$67.75	$67.70
Purchase #6	$136.75	13.436%	$155.1237	$155.12	$155.10	$155.10
Purchase #7	$219.71	11.287%	$244.5087	$244.51	$244.50	$244.50
7 purchase totals =	$900.04		$1,002.2046	$1,002.20	$1,002.15	$1,002.10