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	$227.31	4.469%	$237.4685	$237.47	$237.45	$237.50
Purchase #2	$198.61	7.455%	$213.4164	$213.42	$213.40	$213.40
Purchase #3	$231.62	4.488%	$242.0151	$242.02	$242.00	$242.00
Purchase #4	$141.27	8.624%	$153.4531	$153.45	$153.45	$153.50
Purchase #5	$165.54	13.857%	$188.4789	$188.48	$188.50	$188.50
Purchase #6	$87.62	8.229%	$94.8302	$94.83	$94.85	$94.80
Purchase #7	$145.90	3.103%	$150.4273	$150.43	$150.45	$150.40
7 purchase totals =	$1,197.87		$1,280.0895	$1,280.10	$1,280.10	$1,280.10