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	$211.94	8.353%	$229.6433	$229.64	$229.65	$229.60
Purchase #2	$54.29	6.439%	$57.7857	$57.79	$57.80	$57.80
Purchase #3	$99.43	3.306%	$102.7172	$102.72	$102.70	$102.70
Purchase #4	$245.76	4.616%	$257.1043	$257.10	$257.10	$257.10
Purchase #5	$223.71	13.114%	$253.0473	$253.05	$253.05	$253.00
Purchase #6	$36.64	9.189%	$40.0068	$40.01	$40.00	$40.00
Purchase #7	$140.52	4.188%	$146.405	$146.41	$146.40	$146.40
7 purchase totals =	$1,012.29		$1,086.7096	$1,086.72	$1,086.70	$1,086.60