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	$64.96	6.783%	$69.3662	$69.37	$69.35	$69.40
Purchase #2	$47.93	8.222%	$51.8708	$51.87	$51.85	$51.90
Purchase #3	$54.70	5.865%	$57.9082	$57.91	$57.90	$57.90
Purchase #4	$164.92	6.418%	$175.5046	$175.50	$175.50	$175.50
Purchase #5	$151.91	12.872%	$171.4639	$171.46	$171.45	$171.50
Purchase #6	$162.71	5.165%	$171.114	$171.11	$171.10	$171.10
Purchase #7	$122.49	4.277%	$127.7289	$127.73	$127.75	$127.70
7 purchase totals =	$769.62		$824.9566	$824.95	$824.90	$825.00