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	$32.97	13.538%	$37.4335	$37.43	$37.45	$37.40
Purchase #2	$106.78	7.241%	$114.5119	$114.51	$114.50	$114.50
Purchase #3	$24.27	13.165%	$27.4651	$27.47	$27.45	$27.50
Purchase #4	$98.29	6.223%	$104.4066	$104.41	$104.40	$104.40
Purchase #5	$162.86	13.730%	$185.2207	$185.22	$185.20	$185.20
Purchase #6	$250.41	4.827%	$262.4973	$262.50	$262.50	$262.50
Purchase #7	$119.77	12.445%	$134.6754	$134.68	$134.70	$134.70
7 purchase totals =	$795.35		$866.2105	$866.22	$866.20	$866.20