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	$116.67	9.740%	$128.0337	$128.03	$128.05	$128.00
Purchase #2	$215.38	7.541%	$231.6218	$231.62	$231.60	$231.60
Purchase #3	$76.89	7.585%	$82.7221	$82.72	$82.70	$82.70
Purchase #4	$88.78	10.577%	$98.1703	$98.17	$98.15	$98.20
Purchase #5	$49.57	7.173%	$53.1257	$53.13	$53.15	$53.10
Purchase #6	$90.32	5.579%	$95.359	$95.36	$95.35	$95.40
Purchase #7	$225.79	11.545%	$251.8575	$251.86	$251.85	$251.90
7 purchase totals =	$863.40		$940.8901	$940.89	$940.85	$940.90