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	$174.41	9.328%	$190.679	$190.68	$190.70	$190.70
Purchase #2	$34.61	5.467%	$36.5021	$36.50	$36.50	$36.50
Purchase #3	$42.36	10.515%	$46.8142	$46.81	$46.80	$46.80
Purchase #4	$86.56	7.375%	$92.9438	$92.94	$92.95	$92.90
Purchase #5	$37.89	12.187%	$42.5077	$42.51	$42.50	$42.50
Purchase #6	$118.94	6.358%	$126.5022	$126.50	$126.50	$126.50
Purchase #7	$94.40	11.223%	$104.9945	$104.99	$105.00	$105.00
7 purchase totals =	$589.17		$640.9435	$640.93	$640.95	$640.90