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	$146.96	3.161%	$151.6054	$151.61	$151.60	$151.60
Purchase #2	$223.76	3.359%	$231.2761	$231.28	$231.30	$231.30
Purchase #3	$161.67	3.605%	$167.4982	$167.50	$167.50	$167.50
Purchase #4	$89.75	6.279%	$95.3854	$95.39	$95.40	$95.40
Purchase #5	$33.97	11.811%	$37.9822	$37.98	$38.00	$38.00
Purchase #6	$52.74	12.793%	$59.487	$59.49	$59.50	$59.50
Purchase #7	$217.56	10.333%	$240.0405	$240.04	$240.05	$240.00
7 purchase totals =	$926.41		$983.2748	$983.29	$983.35	$983.30