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	$79.47	11.631%	$88.7132	$88.71	$88.70	$88.70
Purchase #2	$76.35	3.311%	$78.8779	$78.88	$78.90	$78.90
Purchase #3	$216.25	8.874%	$235.44	$235.44	$235.45	$235.40
Purchase #4	$99.83	8.647%	$108.4623	$108.46	$108.45	$108.50
Purchase #5	$105.64	12.612%	$118.9633	$118.96	$118.95	$119.00
Purchase #6	$66.78	8.104%	$72.1919	$72.19	$72.20	$72.20
Purchase #7	$89.57	5.206%	$94.233	$94.23	$94.25	$94.20
7 purchase totals =	$733.89		$796.8816	$796.87	$796.90	$796.90