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	$87.91	10.869%	$97.4649	$97.46	$97.45	$97.50
Purchase #2	$136.98	5.380%	$144.3495	$144.35	$144.35	$144.30
Purchase #3	$72.73	13.337%	$82.43	$82.43	$82.45	$82.40
Purchase #4	$139.41	3.752%	$144.6407	$144.64	$144.65	$144.60
Purchase #5	$236.76	9.219%	$258.5869	$258.59	$258.60	$258.60
Purchase #6	$192.88	4.119%	$200.8247	$200.82	$200.80	$200.80
Purchase #7	$202.82	5.871%	$214.7276	$214.73	$214.75	$214.70
7 purchase totals =	$1,069.49		$1,143.0243	$1,143.02	$1,143.05	$1,142.90