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	$74.43	11.778%	$83.1964	$83.20	$83.20	$83.20
Purchase #2	$140.61	8.121%	$152.0289	$152.03	$152.05	$152.00
Purchase #3	$75.30	13.175%	$85.2208	$85.22	$85.20	$85.20
Purchase #4	$186.45	5.554%	$196.8054	$196.81	$196.80	$196.80
Purchase #5	$91.50	9.285%	$99.9958	$100.00	$100.00	$100.00
Purchase #6	$156.91	10.147%	$172.8317	$172.83	$172.85	$172.80
Purchase #7	$195.88	9.480%	$214.4494	$214.45	$214.45	$214.40
7 purchase totals =	$921.08		$1,004.5284	$1,004.54	$1,004.55	$1,004.40