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	$112.49	9.562%	$123.2463	$123.25	$123.25	$123.20
Purchase #2	$189.52	10.484%	$209.3893	$209.39	$209.40	$209.40
Purchase #3	$202.41	5.188%	$212.911	$212.91	$212.90	$212.90
Purchase #4	$63.42	13.771%	$72.1536	$72.15	$72.15	$72.20
Purchase #5	$76.60	6.366%	$81.4764	$81.48	$81.50	$81.50
Purchase #6	$39.62	8.586%	$43.0218	$43.02	$43.00	$43.00
Purchase #7	$127.94	12.421%	$143.8314	$143.83	$143.85	$143.80
7 purchase totals =	$812.00		$886.0298	$886.03	$886.05	$886.00