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	$187.43	10.151%	$206.456	$206.46	$206.45	$206.50
Purchase #2	$175.35	12.201%	$196.7445	$196.74	$196.75	$196.70
Purchase #3	$90.98	5.598%	$96.0731	$96.07	$96.05	$96.10
Purchase #4	$5.51	3.812%	$5.72	$5.72	$5.70	$5.70
Purchase #5	$92.39	3.867%	$95.9627	$95.96	$95.95	$96.00
Purchase #6	$38.50	12.785%	$43.4222	$43.42	$43.40	$43.40
Purchase #7	$243.50	11.488%	$271.4733	$271.47	$271.45	$271.50
7 purchase totals =	$833.66		$915.8518	$915.84	$915.75	$915.90