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	$231.68	9.627%	$253.9838	$253.98	$254.00	$254.00
Purchase #2	$73.90	10.256%	$81.4792	$81.48	$81.50	$81.50
Purchase #3	$180.77	5.707%	$191.0865	$191.09	$191.10	$191.10
Purchase #4	$54.36	12.312%	$61.0528	$61.05	$61.05	$61.10
Purchase #5	$169.46	10.510%	$187.2702	$187.27	$187.25	$187.30
Purchase #6	$17.68	3.274%	$18.2588	$18.26	$18.25	$18.30
Purchase #7	$88.87	12.308%	$99.8081	$99.81	$99.80	$99.80
7 purchase totals =	$816.72		$892.9394	$892.94	$892.95	$893.10