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	$124.37	13.440%	$141.0853	$141.09	$141.10	$141.10
Purchase #2	$91.98	8.308%	$99.6217	$99.62	$99.60	$99.60
Purchase #3	$122.89	11.476%	$136.9929	$136.99	$137.00	$137.00
Purchase #4	$201.75	10.503%	$222.9398	$222.94	$222.95	$222.90
Purchase #5	$209.97	6.434%	$223.4795	$223.48	$223.50	$223.50
Purchase #6	$200.67	5.821%	$212.351	$212.35	$212.35	$212.40
Purchase #7	$195.81	12.124%	$219.55	$219.55	$219.55	$219.60
7 purchase totals =	$1,147.44		$1,256.0202	$1,256.02	$1,256.05	$1,256.10