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	$172.87	13.644%	$196.4564	$196.46	$196.45	$196.50
Purchase #2	$243.97	5.518%	$257.4323	$257.43	$257.45	$257.40
Purchase #3	$232.27	4.569%	$242.8824	$242.88	$242.90	$242.90
Purchase #4	$181.54	8.259%	$196.5334	$196.53	$196.55	$196.50
Purchase #5	$73.87	13.844%	$84.0966	$84.10	$84.10	$84.10
Purchase #6	$221.89	5.621%	$234.3624	$234.36	$234.35	$234.40
Purchase #7	$120.89	6.373%	$128.5943	$128.59	$128.60	$128.60
7 purchase totals =	$1,247.30		$1,340.3578	$1,340.35	$1,340.40	$1,340.40