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	$78.48	9.196%	$85.697	$85.70	$85.70	$85.70
Purchase #2	$186.82	11.285%	$207.9026	$207.90	$207.90	$207.90
Purchase #3	$136.26	11.222%	$151.5511	$151.55	$151.55	$151.60
Purchase #4	$200.46	13.314%	$227.1492	$227.15	$227.15	$227.10
Purchase #5	$65.52	10.356%	$72.3053	$72.31	$72.30	$72.30
Purchase #6	$206.40	12.590%	$232.3858	$232.39	$232.40	$232.40
Purchase #7	$26.72	12.396%	$30.0322	$30.03	$30.05	$30.00
7 purchase totals =	$900.66		$1,007.0232	$1,007.03	$1,007.05	$1,007.00