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	$153.51	10.390%	$169.4597	$169.46	$169.45	$169.50
Purchase #2	$16.88	6.359%	$17.9534	$17.95	$17.95	$18.00
Purchase #3	$242.69	12.221%	$272.3491	$272.35	$272.35	$272.30
Purchase #4	$35.38	11.385%	$39.408	$39.41	$39.40	$39.40
Purchase #5	$166.39	13.289%	$188.5016	$188.50	$188.50	$188.50
Purchase #6	$73.59	12.562%	$82.8344	$82.83	$82.85	$82.80
Purchase #7	$169.92	9.153%	$185.4728	$185.47	$185.45	$185.50
7 purchase totals =	$858.36		$955.9790	$955.97	$955.95	$956.00