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	$73.77	6.179%	$78.3282	$78.33	$78.35	$78.30
Purchase #2	$162.88	11.811%	$182.1178	$182.12	$182.10	$182.10
Purchase #3	$100.94	4.495%	$105.4773	$105.48	$105.50	$105.50
Purchase #4	$228.67	8.835%	$248.873	$248.87	$248.85	$248.90
Purchase #5	$67.87	6.369%	$72.1926	$72.19	$72.20	$72.20
Purchase #6	$112.47	13.601%	$127.767	$127.77	$127.75	$127.80
Purchase #7	$126.93	11.795%	$141.9014	$141.90	$141.90	$141.90
7 purchase totals =	$873.53		$956.6573	$956.66	$956.65	$956.70