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	$212.89	3.102%	$219.4938	$219.49	$219.50	$219.50
Purchase #2	$181.79	4.826%	$190.5632	$190.56	$190.55	$190.60
Purchase #3	$40.64	3.230%	$41.9527	$41.95	$41.95	$42.00
Purchase #4	$200.49	9.397%	$219.33	$219.33	$219.35	$219.30
Purchase #5	$197.50	5.667%	$208.6923	$208.69	$208.70	$208.70
Purchase #6	$18.44	11.426%	$20.547	$20.55	$20.55	$20.50
Purchase #7	$74.85	3.510%	$77.4772	$77.48	$77.50	$77.50
7 purchase totals =	$926.60		$978.0562	$978.05	$978.10	$978.10