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	$204.52	9.586%	$224.1253	$224.13	$224.15	$224.10
Purchase #2	$32.32	10.829%	$35.8199	$35.82	$35.80	$35.80
Purchase #3	$82.53	4.873%	$86.5517	$86.55	$86.55	$86.60
Purchase #4	$47.42	9.780%	$52.0577	$52.06	$52.05	$52.10
Purchase #5	$160.77	12.127%	$180.2666	$180.27	$180.25	$180.30
Purchase #6	$233.83	7.439%	$251.2246	$251.22	$251.20	$251.20
Purchase #7	$38.76	5.413%	$40.8581	$40.86	$40.85	$40.90
7 purchase totals =	$800.15		$870.9039	$870.91	$870.85	$871.00