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	$195.78	9.272%	$213.9327	$213.93	$213.95	$213.90
Purchase #2	$91.27	11.304%	$101.5872	$101.59	$101.60	$101.60
Purchase #3	$29.34	11.681%	$32.7672	$32.77	$32.75	$32.80
Purchase #4	$81.98	4.297%	$85.5027	$85.50	$85.50	$85.50
Purchase #5	$6.68	12.699%	$7.5283	$7.53	$7.55	$7.50
Purchase #6	$156.55	13.576%	$177.8032	$177.80	$177.80	$177.80
Purchase #7	$147.69	11.227%	$164.2712	$164.27	$164.25	$164.30
7 purchase totals =	$709.29		$783.3925	$783.39	$783.40	$783.40