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	$32.73	13.857%	$37.2654	$37.27	$37.25	$37.30
Purchase #2	$83.33	8.571%	$90.4722	$90.47	$90.45	$90.50
Purchase #3	$184.79	7.433%	$198.5254	$198.53	$198.55	$198.50
Purchase #4	$42.81	5.334%	$45.0935	$45.09	$45.10	$45.10
Purchase #5	$98.96	8.504%	$107.3756	$107.38	$107.40	$107.40
Purchase #6	$227.43	3.184%	$234.6714	$234.67	$234.65	$234.70
Purchase #7	$159.87	5.633%	$168.8755	$168.88	$168.90	$168.90
7 purchase totals =	$829.92		$882.2790	$882.29	$882.30	$882.40