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	$68.27	11.874%	$76.3764	$76.38	$76.40	$76.40
Purchase #2	$77.89	7.345%	$83.611	$83.61	$83.60	$83.60
Purchase #3	$78.59	6.116%	$83.3966	$83.40	$83.40	$83.40
Purchase #4	$37.56	13.849%	$42.7617	$42.76	$42.75	$42.80
Purchase #5	$197.77	7.431%	$212.4663	$212.47	$212.45	$212.50
Purchase #6	$41.64	3.244%	$42.9908	$42.99	$43.00	$43.00
Purchase #7	$84.36	4.266%	$87.9588	$87.96	$87.95	$88.00
7 purchase totals =	$586.08		$629.5616	$629.57	$629.55	$629.70