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	$224.80	9.822%	$246.8799	$246.88	$246.90	$246.90
Purchase #2	$35.52	5.778%	$37.5723	$37.57	$37.55	$37.60
Purchase #3	$56.78	5.721%	$60.0284	$60.03	$60.05	$60.00
Purchase #4	$41.28	9.738%	$45.2998	$45.30	$45.30	$45.30
Purchase #5	$248.65	6.334%	$264.3995	$264.40	$264.40	$264.40
Purchase #6	$101.61	4.301%	$105.9802	$105.98	$106.00	$106.00
Purchase #7	$28.52	4.209%	$29.7204	$29.72	$29.70	$29.70
7 purchase totals =	$737.16		$789.8805	$789.88	$789.90	$789.90