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	$174.55	9.785%	$191.6297	$191.63	$191.65	$191.60
Purchase #2	$94.57	10.533%	$104.5311	$104.53	$104.55	$104.50
Purchase #3	$54.73	12.495%	$61.5685	$61.57	$61.55	$61.60
Purchase #4	$132.63	5.548%	$139.9883	$139.99	$140.00	$140.00
Purchase #5	$89.30	6.434%	$95.0456	$95.05	$95.05	$95.00
Purchase #6	$112.93	12.328%	$126.852	$126.85	$126.85	$126.90
Purchase #7	$147.75	12.139%	$165.6854	$165.69	$165.70	$165.70
7 purchase totals =	$806.46		$885.3006	$885.31	$885.35	$885.30