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	$134.64	11.807%	$150.5369	$150.54	$150.55	$150.50
Purchase #2	$82.34	5.828%	$87.1388	$87.14	$87.15	$87.10
Purchase #3	$237.50	5.813%	$251.3059	$251.31	$251.30	$251.30
Purchase #4	$57.52	7.683%	$61.9393	$61.94	$61.95	$61.90
Purchase #5	$164.79	4.718%	$172.5648	$172.56	$172.55	$172.60
Purchase #6	$241.84	5.194%	$254.4012	$254.40	$254.40	$254.40
Purchase #7	$54.65	3.306%	$56.4567	$56.46	$56.45	$56.50
7 purchase totals =	$973.28		$1,034.3436	$1,034.35	$1,034.35	$1,034.30