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	$47.47	3.110%	$48.9463	$48.95	$48.95	$48.90
Purchase #2	$233.70	9.158%	$255.1022	$255.10	$255.10	$255.10
Purchase #3	$15.30	7.743%	$16.4847	$16.48	$16.50	$16.50
Purchase #4	$149.55	10.272%	$164.9118	$164.91	$164.90	$164.90
Purchase #5	$175.30	5.801%	$185.4692	$185.47	$185.45	$185.50
Purchase #6	$65.79	4.167%	$68.5315	$68.53	$68.55	$68.50
Purchase #7	$180.47	11.254%	$200.7801	$200.78	$200.80	$200.80
7 purchase totals =	$867.58		$940.2258	$940.22	$940.25	$940.20