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	$76.72	10.631%	$84.8761	$84.88	$84.90	$84.90
Purchase #2	$198.53	8.700%	$215.8021	$215.80	$215.80	$215.80
Purchase #3	$89.39	11.492%	$99.6627	$99.66	$99.65	$99.70
Purchase #4	$213.83	6.468%	$227.6605	$227.66	$227.65	$227.70
Purchase #5	$178.63	6.404%	$190.0695	$190.07	$190.05	$190.10
Purchase #6	$36.82	9.715%	$40.3971	$40.40	$40.40	$40.40
Purchase #7	$147.87	9.794%	$162.3524	$162.35	$162.35	$162.40
7 purchase totals =	$941.79		$1,020.8204	$1,020.82	$1,020.80	$1,021.00