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	$116.99	9.334%	$127.9098	$127.91	$127.90	$127.90
Purchase #2	$214.57	13.232%	$242.9619	$242.96	$242.95	$243.00
Purchase #3	$46.83	12.309%	$52.5943	$52.59	$52.60	$52.60
Purchase #4	$81.65	13.686%	$92.8246	$92.82	$92.80	$92.80
Purchase #5	$117.51	10.551%	$129.9085	$129.91	$129.90	$129.90
Purchase #6	$204.28	5.310%	$215.1273	$215.13	$215.15	$215.10
Purchase #7	$74.97	10.487%	$82.8321	$82.83	$82.85	$82.80
7 purchase totals =	$856.80		$944.1585	$944.15	$944.15	$944.10