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	$68.91	3.677%	$71.4438	$71.44	$71.45	$71.40
Purchase #2	$119.95	6.387%	$127.6112	$127.61	$127.60	$127.60
Purchase #3	$80.89	13.226%	$91.5885	$91.59	$91.60	$91.60
Purchase #4	$100.75	8.443%	$109.2563	$109.26	$109.25	$109.30
Purchase #5	$116.48	8.746%	$126.6673	$126.67	$126.65	$126.70
Purchase #6	$90.70	6.804%	$96.8712	$96.87	$96.85	$96.90
Purchase #7	$83.40	10.810%	$92.4155	$92.42	$92.40	$92.40
7 purchase totals =	$661.08		$715.8538	$715.86	$715.80	$715.90