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	$232.71	7.492%	$250.1446	$250.14	$250.15	$250.10
Purchase #2	$152.47	10.118%	$167.8969	$167.90	$167.90	$167.90
Purchase #3	$147.41	11.284%	$164.0437	$164.04	$164.05	$164.00
Purchase #4	$216.31	13.200%	$244.8629	$244.86	$244.85	$244.90
Purchase #5	$114.56	3.667%	$118.7609	$118.76	$118.75	$118.80
Purchase #6	$87.39	4.863%	$91.6398	$91.64	$91.65	$91.60
Purchase #7	$144.84	11.270%	$161.1635	$161.16	$161.15	$161.20
7 purchase totals =	$1,095.69		$1,198.5123	$1,198.50	$1,198.50	$1,198.50