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	$177.77	4.550%	$185.8585	$185.86	$185.85	$185.90
Purchase #2	$63.57	4.752%	$66.5908	$66.59	$66.60	$66.60
Purchase #3	$69.91	9.798%	$76.7598	$76.76	$76.75	$76.80
Purchase #4	$17.74	4.199%	$18.4849	$18.48	$18.50	$18.50
Purchase #5	$87.44	13.387%	$99.1456	$99.15	$99.15	$99.10
Purchase #6	$112.47	13.230%	$127.3498	$127.35	$127.35	$127.30
Purchase #7	$192.41	7.495%	$206.8311	$206.83	$206.85	$206.80
7 purchase totals =	$721.31		$781.0205	$781.02	$781.05	$781.00