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	$205.82	13.738%	$234.0956	$234.10	$234.10	$234.10
Purchase #2	$37.72	9.577%	$41.3324	$41.33	$41.35	$41.30
Purchase #3	$157.94	7.445%	$169.6986	$169.70	$169.70	$169.70
Purchase #4	$78.27	13.547%	$88.8732	$88.87	$88.85	$88.90
Purchase #5	$21.86	5.346%	$23.0286	$23.03	$23.05	$23.00
Purchase #6	$67.46	7.646%	$72.618	$72.62	$72.60	$72.60
Purchase #7	$68.34	5.142%	$71.854	$71.85	$71.85	$71.90
7 purchase totals =	$637.41		$701.5004	$701.50	$701.50	$701.50