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	$42.81	11.221%	$47.6137	$47.61	$47.60	$47.60
Purchase #2	$31.93	3.828%	$33.1523	$33.15	$33.15	$33.20
Purchase #3	$27.90	13.427%	$31.6461	$31.65	$31.65	$31.60
Purchase #4	$32.34	3.339%	$33.4198	$33.42	$33.40	$33.40
Purchase #5	$191.27	3.620%	$198.194	$198.19	$198.20	$198.20
Purchase #6	$229.69	11.150%	$255.3004	$255.30	$255.30	$255.30
Purchase #7	$66.72	9.847%	$73.2899	$73.29	$73.30	$73.30
7 purchase totals =	$622.66		$672.6162	$672.61	$672.60	$672.60