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	$23.31	8.342%	$25.2545	$25.25	$25.25	$25.30
Purchase #2	$249.91	11.834%	$279.4843	$279.48	$279.50	$279.50
Purchase #3	$166.44	3.248%	$171.846	$171.85	$171.85	$171.80
Purchase #4	$110.91	5.789%	$117.3306	$117.33	$117.35	$117.30
Purchase #5	$247.37	13.552%	$280.8936	$280.89	$280.90	$280.90
Purchase #6	$68.69	5.284%	$72.3196	$72.32	$72.30	$72.30
Purchase #7	$238.44	3.580%	$246.9762	$246.98	$247.00	$247.00
7 purchase totals =	$1,105.07		$1,194.1048	$1,194.10	$1,194.15	$1,194.10