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	$165.79	11.836%	$185.4129	$185.41	$185.40	$185.40
Purchase #2	$164.46	12.385%	$184.8284	$184.83	$184.85	$184.80
Purchase #3	$172.66	4.600%	$180.6024	$180.60	$180.60	$180.60
Purchase #4	$230.39	8.805%	$250.6758	$250.68	$250.70	$250.70
Purchase #5	$224.54	3.154%	$231.622	$231.62	$231.60	$231.60
Purchase #6	$139.48	3.528%	$144.4009	$144.40	$144.40	$144.40
Purchase #7	$145.26	3.524%	$150.379	$150.38	$150.40	$150.40
7 purchase totals =	$1,242.58		$1,327.9214	$1,327.92	$1,327.95	$1,327.90