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	$199.57	11.756%	$223.0314	$223.03	$223.05	$223.00
Purchase #2	$143.95	3.195%	$148.5492	$148.55	$148.55	$148.50
Purchase #3	$124.65	13.548%	$141.5376	$141.54	$141.55	$141.50
Purchase #4	$86.28	3.175%	$89.0194	$89.02	$89.00	$89.00
Purchase #5	$46.37	7.590%	$49.8895	$49.89	$49.90	$49.90
Purchase #6	$197.32	4.166%	$205.5404	$205.54	$205.55	$205.50
Purchase #7	$150.34	4.588%	$157.2376	$157.24	$157.25	$157.20
7 purchase totals =	$948.48		$1,014.8051	$1,014.81	$1,014.85	$1,014.60