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	$244.98	8.260%	$265.2153	$265.22	$265.20	$265.20
Purchase #2	$94.50	10.459%	$104.3838	$104.38	$104.40	$104.40
Purchase #3	$131.96	6.679%	$140.7736	$140.77	$140.75	$140.80
Purchase #4	$137.59	9.347%	$150.4505	$150.45	$150.45	$150.50
Purchase #5	$232.89	12.616%	$262.2714	$262.27	$262.25	$262.30
Purchase #6	$35.30	13.622%	$40.1086	$40.11	$40.10	$40.10
Purchase #7	$127.51	11.546%	$142.2323	$142.23	$142.25	$142.20
7 purchase totals =	$1,004.73		$1,105.4355	$1,105.43	$1,105.40	$1,105.50