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	$48.84	8.322%	$52.9045	$52.90	$52.90	$52.90
Purchase #2	$17.90	10.593%	$19.7961	$19.80	$19.80	$19.80
Purchase #3	$88.52	7.830%	$95.4511	$95.45	$95.45	$95.50
Purchase #4	$92.35	11.753%	$103.2039	$103.20	$103.20	$103.20
Purchase #5	$146.73	3.608%	$152.024	$152.02	$152.00	$152.00
Purchase #6	$42.92	11.575%	$47.888	$47.89	$47.90	$47.90
Purchase #7	$30.63	12.411%	$34.4315	$34.43	$34.45	$34.40
7 purchase totals =	$467.89		$505.6991	$505.69	$505.70	$505.70