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	$209.74	6.770%	$223.9394	$223.94	$223.95	$223.90
Purchase #2	$92.48	9.680%	$101.4321	$101.43	$101.45	$101.40
Purchase #3	$33.28	8.869%	$36.2316	$36.23	$36.25	$36.20
Purchase #4	$30.78	6.866%	$32.8934	$32.89	$32.90	$32.90
Purchase #5	$235.90	3.663%	$244.541	$244.54	$244.55	$244.50
Purchase #6	$211.67	3.250%	$218.5493	$218.55	$218.55	$218.50
Purchase #7	$134.76	7.505%	$144.8737	$144.87	$144.85	$144.90
7 purchase totals =	$948.61		$1,002.4605	$1,002.45	$1,002.50	$1,002.30