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	$85.89	7.350%	$92.2029	$92.20	$92.20	$92.20
Purchase #2	$180.65	6.487%	$192.3688	$192.37	$192.35	$192.40
Purchase #3	$102.31	9.329%	$111.8545	$111.85	$111.85	$111.90
Purchase #4	$34.52	4.172%	$35.9602	$35.96	$35.95	$36.00
Purchase #5	$152.87	12.750%	$172.3609	$172.36	$172.35	$172.40
Purchase #6	$170.44	12.219%	$191.2661	$191.27	$191.25	$191.30
Purchase #7	$142.96	13.154%	$161.765	$161.77	$161.75	$161.80
7 purchase totals =	$869.64		$957.7784	$957.78	$957.70	$958.00