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	$64.42	5.417%	$67.9096	$67.91	$67.90	$67.90
Purchase #2	$84.85	13.261%	$96.102	$96.10	$96.10	$96.10
Purchase #3	$109.72	13.410%	$124.4335	$124.43	$124.45	$124.40
Purchase #4	$20.84	4.559%	$21.7901	$21.79	$21.80	$21.80
Purchase #5	$11.87	5.840%	$12.5632	$12.56	$12.55	$12.60
Purchase #6	$104.61	9.694%	$114.7509	$114.75	$114.75	$114.80
Purchase #7	$44.75	13.868%	$50.9559	$50.96	$50.95	$51.00
7 purchase totals =	$441.06		$488.5052	$488.50	$488.50	$488.60