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	$119.73	10.656%	$132.4884	$132.49	$132.50	$132.50
Purchase #2	$172.59	12.491%	$194.1482	$194.15	$194.15	$194.10
Purchase #3	$179.58	6.749%	$191.6999	$191.70	$191.70	$191.70
Purchase #4	$102.30	9.183%	$111.6942	$111.69	$111.70	$111.70
Purchase #5	$67.34	11.806%	$75.2902	$75.29	$75.30	$75.30
Purchase #6	$18.82	6.372%	$20.0192	$20.02	$20.00	$20.00
Purchase #7	$203.41	6.308%	$216.2411	$216.24	$216.25	$216.20
7 purchase totals =	$863.77		$941.5812	$941.58	$941.60	$941.50