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	$81.25	12.680%	$91.5525	$91.55	$91.55	$91.60
Purchase #2	$35.27	13.568%	$40.0554	$40.06	$40.05	$40.10
Purchase #3	$29.86	10.300%	$32.9356	$32.94	$32.95	$32.90
Purchase #4	$244.54	9.211%	$267.0646	$267.06	$267.05	$267.10
Purchase #5	$250.35	3.183%	$258.3186	$258.32	$258.30	$258.30
Purchase #6	$214.37	5.366%	$225.8731	$225.87	$225.85	$225.90
Purchase #7	$94.96	9.652%	$104.1255	$104.13	$104.15	$104.10
7 purchase totals =	$950.60		$1,019.9253	$1,019.93	$1,019.90	$1,020.00