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	$201.98	10.413%	$223.0122	$223.01	$223.00	$223.00
Purchase #2	$10.70	6.373%	$11.3819	$11.38	$11.40	$11.40
Purchase #3	$222.98	9.509%	$244.1832	$244.18	$244.20	$244.20
Purchase #4	$63.97	5.270%	$67.3412	$67.34	$67.35	$67.30
Purchase #5	$94.78	11.284%	$105.475	$105.48	$105.50	$105.50
Purchase #6	$200.80	5.283%	$211.4083	$211.41	$211.40	$211.40
Purchase #7	$64.63	4.613%	$67.6114	$67.61	$67.60	$67.60
7 purchase totals =	$859.84		$930.4132	$930.41	$930.45	$930.40