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	$119.54	5.494%	$126.1075	$126.11	$126.10	$126.10
Purchase #2	$233.36	11.582%	$260.3878	$260.39	$260.40	$260.40
Purchase #3	$150.43	10.318%	$165.9514	$165.95	$165.95	$166.00
Purchase #4	$175.81	8.228%	$190.2756	$190.28	$190.30	$190.30
Purchase #5	$153.85	13.867%	$175.1844	$175.18	$175.20	$175.20
Purchase #6	$39.89	5.589%	$42.1195	$42.12	$42.10	$42.10
Purchase #7	$42.61	3.600%	$44.144	$44.14	$44.15	$44.10
7 purchase totals =	$915.49		$1,004.1702	$1,004.17	$1,004.20	$1,004.20