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	$166.47	3.517%	$172.3247	$172.32	$172.30	$172.30
Purchase #2	$206.64	13.169%	$233.8524	$233.85	$233.85	$233.90
Purchase #3	$238.35	5.330%	$251.0541	$251.05	$251.05	$251.10
Purchase #4	$192.82	8.340%	$208.9012	$208.90	$208.90	$208.90
Purchase #5	$72.64	6.319%	$77.2301	$77.23	$77.25	$77.20
Purchase #6	$189.64	5.397%	$199.8749	$199.87	$199.85	$199.90
Purchase #7	$37.27	7.143%	$39.9322	$39.93	$39.95	$39.90
7 purchase totals =	$1,103.83		$1,183.1696	$1,183.15	$1,183.15	$1,183.20