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	$208.97	6.659%	$222.8853	$222.89	$222.90	$222.90
Purchase #2	$232.57	11.478%	$259.2644	$259.26	$259.25	$259.30
Purchase #3	$26.34	7.778%	$28.3887	$28.39	$28.40	$28.40
Purchase #4	$143.67	7.752%	$154.8073	$154.81	$154.80	$154.80
Purchase #5	$114.68	3.722%	$118.9484	$118.95	$118.95	$118.90
Purchase #6	$219.44	4.451%	$229.2073	$229.21	$229.20	$229.20
Purchase #7	$37.37	13.229%	$42.3137	$42.31	$42.30	$42.30
7 purchase totals =	$983.04		$1,055.8151	$1,055.82	$1,055.80	$1,055.80