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	$133.56	7.107%	$143.0521	$143.05	$143.05	$143.10
Purchase #2	$196.72	10.359%	$217.0982	$217.10	$217.10	$217.10
Purchase #3	$146.98	4.646%	$153.8087	$153.81	$153.80	$153.80
Purchase #4	$73.74	11.343%	$82.1043	$82.10	$82.10	$82.10
Purchase #5	$154.43	5.438%	$162.8279	$162.83	$162.85	$162.80
Purchase #6	$196.55	6.857%	$210.0274	$210.03	$210.05	$210.00
Purchase #7	$155.39	4.506%	$162.3919	$162.39	$162.40	$162.40
7 purchase totals =	$1,057.37		$1,131.3105	$1,131.31	$1,131.35	$1,131.30