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	$186.99	11.729%	$208.9221	$208.92	$208.90	$208.90
Purchase #2	$37.76	12.564%	$42.5042	$42.50	$42.50	$42.50
Purchase #3	$129.37	5.779%	$136.8463	$136.85	$136.85	$136.80
Purchase #4	$247.29	4.692%	$258.8928	$258.89	$258.90	$258.90
Purchase #5	$26.51	3.131%	$27.34	$27.34	$27.35	$27.30
Purchase #6	$198.55	11.649%	$221.6791	$221.68	$221.70	$221.70
Purchase #7	$137.83	13.569%	$156.5322	$156.53	$156.55	$156.50
7 purchase totals =	$964.30		$1,052.7167	$1,052.71	$1,052.75	$1,052.60