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	$108.43	3.191%	$111.89	$111.89	$111.90	$111.90
Purchase #2	$13.63	11.333%	$15.1747	$15.17	$15.15	$15.20
Purchase #3	$85.61	12.604%	$96.4003	$96.40	$96.40	$96.40
Purchase #4	$20.77	12.541%	$23.3748	$23.37	$23.35	$23.40
Purchase #5	$246.47	10.720%	$272.8916	$272.89	$272.90	$272.90
Purchase #6	$205.29	3.494%	$212.4628	$212.46	$212.45	$212.50
Purchase #7	$112.57	6.144%	$119.4863	$119.49	$119.50	$119.50
7 purchase totals =	$792.77		$851.6805	$851.67	$851.65	$851.80