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	$147.98	11.267%	$164.6529	$164.65	$164.65	$164.70
Purchase #2	$95.53	10.596%	$105.6524	$105.65	$105.65	$105.70
Purchase #3	$37.95	4.662%	$39.7192	$39.72	$39.70	$39.70
Purchase #4	$52.67	13.661%	$59.8652	$59.87	$59.85	$59.90
Purchase #5	$234.85	4.697%	$245.8809	$245.88	$245.90	$245.90
Purchase #6	$248.57	7.777%	$267.9013	$267.90	$267.90	$267.90
Purchase #7	$28.77	7.495%	$30.9263	$30.93	$30.95	$30.90
7 purchase totals =	$846.32		$914.5982	$914.60	$914.60	$914.70