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	$206.78	7.844%	$222.9998	$223.00	$223.00	$223.00
Purchase #2	$118.47	3.406%	$122.5051	$122.51	$122.50	$122.50
Purchase #3	$54.78	8.702%	$59.547	$59.55	$59.55	$59.50
Purchase #4	$48.34	4.528%	$50.5288	$50.53	$50.55	$50.50
Purchase #5	$178.29	4.138%	$185.6676	$185.67	$185.65	$185.70
Purchase #6	$242.94	5.700%	$256.7876	$256.79	$256.80	$256.80
Purchase #7	$218.93	11.141%	$243.321	$243.32	$243.30	$243.30
7 purchase totals =	$1,068.53		$1,141.3569	$1,141.37	$1,141.35	$1,141.30