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	$104.49	7.297%	$112.1146	$112.11	$112.10	$112.10
Purchase #2	$83.82	7.181%	$89.8391	$89.84	$89.85	$89.80
Purchase #3	$238.45	9.189%	$260.3612	$260.36	$260.35	$260.40
Purchase #4	$225.70	10.818%	$250.1162	$250.12	$250.10	$250.10
Purchase #5	$102.47	4.827%	$107.4162	$107.42	$107.40	$107.40
Purchase #6	$239.32	7.220%	$256.5989	$256.60	$256.60	$256.60
Purchase #7	$187.57	11.490%	$209.1218	$209.12	$209.10	$209.10
7 purchase totals =	$1,181.82		$1,285.5680	$1,285.57	$1,285.50	$1,285.50