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	$61.34	9.176%	$66.9686	$66.97	$66.95	$67.00
Purchase #2	$242.86	11.141%	$269.917	$269.92	$269.90	$269.90
Purchase #3	$83.57	6.226%	$88.7731	$88.77	$88.75	$88.80
Purchase #4	$70.72	9.205%	$77.2298	$77.23	$77.25	$77.20
Purchase #5	$57.66	7.285%	$61.8605	$61.86	$61.85	$61.90
Purchase #6	$38.48	9.558%	$42.1579	$42.16	$42.15	$42.20
Purchase #7	$155.33	12.783%	$175.1858	$175.19	$175.20	$175.20
7 purchase totals =	$709.96		$782.0927	$782.10	$782.05	$782.20