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	$79.74	3.566%	$82.5835	$82.58	$82.60	$82.60
Purchase #2	$197.76	12.181%	$221.8491	$221.85	$221.85	$221.80
Purchase #3	$145.93	13.368%	$165.4379	$165.44	$165.45	$165.40
Purchase #4	$158.40	5.863%	$167.687	$167.69	$167.70	$167.70
Purchase #5	$227.61	5.645%	$240.4586	$240.46	$240.45	$240.50
Purchase #6	$124.95	7.505%	$134.3275	$134.33	$134.35	$134.30
Purchase #7	$32.83	3.733%	$34.0555	$34.06	$34.05	$34.10
7 purchase totals =	$967.22		$1,046.3991	$1,046.41	$1,046.45	$1,046.40