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	$248.98	10.817%	$275.9122	$275.91	$275.90	$275.90
Purchase #2	$96.81	7.673%	$104.2382	$104.24	$104.25	$104.20
Purchase #3	$77.29	10.721%	$85.5763	$85.58	$85.60	$85.60
Purchase #4	$159.62	9.451%	$174.7057	$174.71	$174.70	$174.70
Purchase #5	$51.78	3.347%	$53.5131	$53.51	$53.50	$53.50
Purchase #6	$29.70	9.320%	$32.468	$32.47	$32.45	$32.50
Purchase #7	$242.47	5.609%	$256.0701	$256.07	$256.05	$256.10
7 purchase totals =	$906.65		$982.4836	$982.49	$982.45	$982.50