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	$87.65	4.707%	$91.7757	$91.78	$91.80	$91.80
Purchase #2	$113.81	11.598%	$127.0097	$127.01	$127.00	$127.00
Purchase #3	$245.38	6.504%	$261.3395	$261.34	$261.35	$261.30
Purchase #4	$87.40	11.374%	$97.3409	$97.34	$97.35	$97.30
Purchase #5	$85.53	12.126%	$95.9014	$95.90	$95.90	$95.90
Purchase #6	$243.99	5.684%	$257.8584	$257.86	$257.85	$257.90
Purchase #7	$68.60	3.760%	$71.1794	$71.18	$71.20	$71.20
7 purchase totals =	$932.36		$1,002.4050	$1,002.41	$1,002.45	$1,002.40