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	$53.59	10.372%	$59.1484	$59.15	$59.15	$59.10
Purchase #2	$92.29	3.726%	$95.7287	$95.73	$95.75	$95.70
Purchase #3	$243.55	12.743%	$274.5856	$274.59	$274.60	$274.60
Purchase #4	$223.88	5.763%	$236.7822	$236.78	$236.80	$236.80
Purchase #5	$233.52	5.276%	$245.8405	$245.84	$245.85	$245.80
Purchase #6	$92.67	11.688%	$103.5013	$103.50	$103.50	$103.50
Purchase #7	$169.98	6.448%	$180.9403	$180.94	$180.95	$180.90
7 purchase totals =	$1,109.48		$1,196.5270	$1,196.53	$1,196.60	$1,196.40