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	$152.78	7.467%	$164.1881	$164.19	$164.20	$164.20
Purchase #2	$57.47	3.501%	$59.482	$59.48	$59.50	$59.50
Purchase #3	$188.83	4.527%	$197.3783	$197.38	$197.40	$197.40
Purchase #4	$79.96	10.254%	$88.1591	$88.16	$88.15	$88.20
Purchase #5	$69.35	13.217%	$78.516	$78.52	$78.50	$78.50
Purchase #6	$101.99	6.551%	$108.6714	$108.67	$108.65	$108.70
Purchase #7	$87.33	8.742%	$94.9644	$94.96	$94.95	$95.00
7 purchase totals =	$737.71		$791.3593	$791.36	$791.35	$791.50