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	$83.82	11.678%	$93.6085	$93.61	$93.60	$93.60
Purchase #2	$174.77	5.300%	$184.0328	$184.03	$184.05	$184.00
Purchase #3	$95.61	4.438%	$99.8532	$99.85	$99.85	$99.90
Purchase #4	$69.36	13.617%	$78.8048	$78.80	$78.80	$78.80
Purchase #5	$167.91	8.476%	$182.1421	$182.14	$182.15	$182.10
Purchase #6	$217.91	11.453%	$242.8672	$242.87	$242.85	$242.90
Purchase #7	$90.67	11.187%	$100.8133	$100.81	$100.80	$100.80
7 purchase totals =	$900.05		$982.1219	$982.11	$982.10	$982.10