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	$190.43	10.740%	$210.8822	$210.88	$210.90	$210.90
Purchase #2	$86.61	5.508%	$91.3805	$91.38	$91.40	$91.40
Purchase #3	$88.63	11.195%	$98.5521	$98.55	$98.55	$98.60
Purchase #4	$114.53	12.167%	$128.4649	$128.46	$128.45	$128.50
Purchase #5	$143.96	4.246%	$150.0725	$150.07	$150.05	$150.10
Purchase #6	$217.25	4.568%	$227.174	$227.17	$227.15	$227.20
Purchase #7	$26.90	13.443%	$30.5162	$30.52	$30.50	$30.50
7 purchase totals =	$868.31		$937.0424	$937.03	$937.00	$937.20