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	$130.70	13.495%	$148.338	$148.34	$148.35	$148.30
Purchase #2	$5.54	11.454%	$6.1746	$6.17	$6.15	$6.20
Purchase #3	$244.81	5.581%	$258.4728	$258.47	$258.45	$258.50
Purchase #4	$142.84	13.638%	$162.3205	$162.32	$162.30	$162.30
Purchase #5	$6.45	6.847%	$6.8916	$6.89	$6.90	$6.90
Purchase #6	$215.70	3.577%	$223.4156	$223.42	$223.40	$223.40
Purchase #7	$76.50	9.504%	$83.7706	$83.77	$83.75	$83.80
7 purchase totals =	$822.54		$889.3837	$889.38	$889.30	$889.40