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	$66.58	8.854%	$72.475	$72.48	$72.50	$72.50
Purchase #2	$58.35	5.516%	$61.5686	$61.57	$61.55	$61.60
Purchase #3	$82.69	13.696%	$94.0152	$94.02	$94.00	$94.00
Purchase #4	$85.32	5.375%	$89.906	$89.91	$89.90	$89.90
Purchase #5	$177.29	4.186%	$184.7114	$184.71	$184.70	$184.70
Purchase #6	$63.54	9.388%	$69.5051	$69.51	$69.50	$69.50
Purchase #7	$239.45	5.163%	$251.8128	$251.81	$251.80	$251.80
7 purchase totals =	$773.22		$823.9941	$824.01	$823.95	$824.00