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	$139.55	13.552%	$158.4618	$158.46	$158.45	$158.50
Purchase #2	$74.39	11.142%	$82.6785	$82.68	$82.70	$82.70
Purchase #3	$42.58	6.829%	$45.4878	$45.49	$45.50	$45.50
Purchase #4	$53.63	4.669%	$56.134	$56.13	$56.15	$56.10
Purchase #5	$190.32	8.364%	$206.2384	$206.24	$206.25	$206.20
Purchase #6	$84.38	3.661%	$87.4692	$87.47	$87.45	$87.50
Purchase #7	$69.81	9.557%	$76.4817	$76.48	$76.50	$76.50
7 purchase totals =	$654.66		$712.9514	$712.95	$713.00	$713.00