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	$137.65	8.853%	$149.8362	$149.84	$149.85	$149.80
Purchase #2	$210.96	6.732%	$225.1618	$225.16	$225.15	$225.20
Purchase #3	$108.55	7.360%	$116.5393	$116.54	$116.55	$116.50
Purchase #4	$223.25	13.693%	$253.8196	$253.82	$253.80	$253.80
Purchase #5	$76.73	11.274%	$85.3805	$85.38	$85.40	$85.40
Purchase #6	$127.56	4.334%	$133.0885	$133.09	$133.10	$133.10
Purchase #7	$38.96	4.667%	$40.7783	$40.78	$40.80	$40.80
7 purchase totals =	$923.66		$1,004.6042	$1,004.61	$1,004.65	$1,004.60