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	$176.89	6.224%	$187.8996	$187.90	$187.90	$187.90
Purchase #2	$55.49	11.548%	$61.898	$61.90	$61.90	$61.90
Purchase #3	$199.55	12.136%	$223.7674	$223.77	$223.75	$223.80
Purchase #4	$220.73	9.302%	$241.2623	$241.26	$241.25	$241.30
Purchase #5	$104.37	13.124%	$118.0675	$118.07	$118.05	$118.10
Purchase #6	$147.74	8.304%	$160.0083	$160.01	$160.00	$160.00
Purchase #7	$38.77	12.152%	$43.4813	$43.48	$43.50	$43.50
7 purchase totals =	$943.54		$1,036.3844	$1,036.39	$1,036.35	$1,036.50