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	$98.50	4.477%	$102.9098	$102.91	$102.90	$102.90
Purchase #2	$219.44	9.575%	$240.4514	$240.45	$240.45	$240.50
Purchase #3	$147.29	10.385%	$162.5861	$162.59	$162.60	$162.60
Purchase #4	$151.49	7.306%	$162.5579	$162.56	$162.55	$162.60
Purchase #5	$188.72	12.870%	$213.0083	$213.01	$213.00	$213.00
Purchase #6	$87.61	8.330%	$94.9079	$94.91	$94.90	$94.90
Purchase #7	$242.97	5.765%	$256.9772	$256.98	$257.00	$257.00
7 purchase totals =	$1,136.02		$1,233.3986	$1,233.41	$1,233.40	$1,233.50