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	$178.71	7.722%	$192.51	$192.51	$192.50	$192.50
Purchase #2	$238.37	6.620%	$254.1501	$254.15	$254.15	$254.20
Purchase #3	$31.62	11.367%	$35.2142	$35.21	$35.20	$35.20
Purchase #4	$182.39	9.345%	$199.4343	$199.43	$199.45	$199.40
Purchase #5	$209.39	10.871%	$232.1528	$232.15	$232.15	$232.20
Purchase #6	$90.25	11.194%	$100.3526	$100.35	$100.35	$100.40
Purchase #7	$141.42	6.502%	$150.6151	$150.62	$150.60	$150.60
7 purchase totals =	$1,072.15		$1,164.4291	$1,164.42	$1,164.40	$1,164.50