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	$125.95	13.262%	$142.6535	$142.65	$142.65	$142.70
Purchase #2	$83.78	5.346%	$88.2589	$88.26	$88.25	$88.30
Purchase #3	$131.59	4.717%	$137.7971	$137.80	$137.80	$137.80
Purchase #4	$47.28	5.787%	$50.0161	$50.02	$50.00	$50.00
Purchase #5	$98.38	5.403%	$103.6955	$103.70	$103.70	$103.70
Purchase #6	$5.34	3.130%	$5.5071	$5.51	$5.50	$5.50
Purchase #7	$125.33	11.373%	$139.5838	$139.58	$139.60	$139.60
7 purchase totals =	$617.65		$667.5120	$667.52	$667.50	$667.60