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	$138.50	4.617%	$144.8945	$144.89	$144.90	$144.90
Purchase #2	$7.36	7.288%	$7.8964	$7.90	$7.90	$7.90
Purchase #3	$53.89	6.813%	$57.5615	$57.56	$57.55	$57.60
Purchase #4	$9.64	11.821%	$10.7795	$10.78	$10.80	$10.80
Purchase #5	$222.62	4.795%	$233.2946	$233.29	$233.30	$233.30
Purchase #6	$200.98	13.124%	$227.3566	$227.36	$227.35	$227.40
Purchase #7	$29.67	5.400%	$31.2722	$31.27	$31.25	$31.30
7 purchase totals =	$662.66		$713.0553	$713.05	$713.05	$713.20