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	$155.73	10.663%	$172.3355	$172.34	$172.35	$172.30
Purchase #2	$212.43	13.726%	$241.5881	$241.59	$241.60	$241.60
Purchase #3	$158.88	13.267%	$179.9586	$179.96	$179.95	$180.00
Purchase #4	$225.89	7.817%	$243.5478	$243.55	$243.55	$243.50
Purchase #5	$194.81	3.449%	$201.529	$201.53	$201.55	$201.50
Purchase #6	$131.69	7.441%	$141.4891	$141.49	$141.50	$141.50
Purchase #7	$182.78	4.700%	$191.3707	$191.37	$191.35	$191.40
7 purchase totals =	$1,262.21		$1,371.8188	$1,371.83	$1,371.85	$1,371.80