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	$115.31	9.566%	$126.3406	$126.34	$126.35	$126.30
Purchase #2	$135.34	11.664%	$151.1261	$151.13	$151.15	$151.10
Purchase #3	$184.97	13.493%	$209.928	$209.93	$209.95	$209.90
Purchase #4	$72.38	13.343%	$82.0377	$82.04	$82.05	$82.00
Purchase #5	$63.61	5.290%	$66.975	$66.98	$67.00	$67.00
Purchase #6	$68.27	5.545%	$72.0556	$72.06	$72.05	$72.10
Purchase #7	$28.58	9.663%	$31.3417	$31.34	$31.35	$31.30
7 purchase totals =	$668.46		$739.8047	$739.82	$739.90	$739.70