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	$195.81	12.262%	$219.8202	$219.82	$219.80	$219.80
Purchase #2	$237.53	10.393%	$262.2165	$262.22	$262.20	$262.20
Purchase #3	$103.72	7.694%	$111.7002	$111.70	$111.70	$111.70
Purchase #4	$164.44	9.686%	$180.3677	$180.37	$180.35	$180.40
Purchase #5	$18.97	10.531%	$20.9677	$20.97	$20.95	$21.00
Purchase #6	$35.61	4.811%	$37.3232	$37.32	$37.30	$37.30
Purchase #7	$173.36	9.542%	$189.902	$189.90	$189.90	$189.90
7 purchase totals =	$929.44		$1,022.2975	$1,022.30	$1,022.20	$1,022.30