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	$100.77	8.560%	$109.3959	$109.40	$109.40	$109.40
Purchase #2	$19.93	9.186%	$21.7608	$21.76	$21.75	$21.80
Purchase #3	$109.57	3.629%	$113.5463	$113.55	$113.55	$113.50
Purchase #4	$239.89	6.757%	$256.0994	$256.10	$256.10	$256.10
Purchase #5	$12.82	3.641%	$13.2868	$13.29	$13.30	$13.30
Purchase #6	$219.98	3.869%	$228.491	$228.49	$228.50	$228.50
Purchase #7	$176.80	6.657%	$188.5696	$188.57	$188.55	$188.60
7 purchase totals =	$879.76		$931.1498	$931.16	$931.15	$931.20