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	$126.50	10.572%	$139.8736	$139.87	$139.85	$139.90
Purchase #2	$100.84	8.231%	$109.1401	$109.14	$109.15	$109.10
Purchase #3	$170.72	11.478%	$190.3152	$190.32	$190.30	$190.30
Purchase #4	$134.37	10.497%	$148.4748	$148.47	$148.45	$148.50
Purchase #5	$148.34	12.232%	$166.4849	$166.48	$166.50	$166.50
Purchase #6	$245.94	11.851%	$275.0863	$275.09	$275.10	$275.10
Purchase #7	$246.53	10.200%	$271.6761	$271.68	$271.70	$271.70
7 purchase totals =	$1,173.24		$1,301.0510	$1,301.05	$1,301.05	$1,301.10