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	$218.41	10.162%	$240.6048	$240.60	$240.60	$240.60
Purchase #2	$142.32	7.356%	$152.7891	$152.79	$152.80	$152.80
Purchase #3	$69.99	3.219%	$72.243	$72.24	$72.25	$72.20
Purchase #4	$36.29	10.276%	$40.0192	$40.02	$40.00	$40.00
Purchase #5	$50.29	8.641%	$54.6356	$54.64	$54.65	$54.60
Purchase #6	$188.41	13.212%	$213.3027	$213.30	$213.30	$213.30
Purchase #7	$161.69	3.212%	$166.8835	$166.88	$166.90	$166.90
7 purchase totals =	$867.40		$940.4779	$940.47	$940.50	$940.40