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	$195.35	8.770%	$212.4822	$212.48	$212.50	$212.50
Purchase #2	$79.61	5.147%	$83.7075	$83.71	$83.70	$83.70
Purchase #3	$34.55	9.691%	$37.8982	$37.90	$37.90	$37.90
Purchase #4	$37.83	11.574%	$42.2084	$42.21	$42.20	$42.20
Purchase #5	$71.50	9.681%	$78.4219	$78.42	$78.40	$78.40
Purchase #6	$46.78	11.698%	$52.2523	$52.25	$52.25	$52.30
Purchase #7	$56.70	13.632%	$64.4293	$64.43	$64.45	$64.40
7 purchase totals =	$522.32		$571.3998	$571.40	$571.40	$571.40