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	$29.69	9.556%	$32.5272	$32.53	$32.55	$32.50
Purchase #2	$26.94	7.780%	$29.0359	$29.04	$29.05	$29.00
Purchase #3	$139.77	4.730%	$146.3811	$146.38	$146.40	$146.40
Purchase #4	$176.82	6.395%	$188.1276	$188.13	$188.15	$188.10
Purchase #5	$191.38	12.792%	$215.8613	$215.86	$215.85	$215.90
Purchase #6	$89.97	6.372%	$95.7029	$95.70	$95.70	$95.70
Purchase #7	$104.50	13.266%	$118.363	$118.36	$118.35	$118.40
7 purchase totals =	$759.07		$825.9990	$826.00	$826.05	$826.00