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	$215.68	5.241%	$226.9838	$226.98	$227.00	$227.00
Purchase #2	$89.71	11.580%	$100.0984	$100.10	$100.10	$100.10
Purchase #3	$130.66	5.297%	$137.5811	$137.58	$137.60	$137.60
Purchase #4	$77.67	13.430%	$88.1011	$88.10	$88.10	$88.10
Purchase #5	$144.47	7.296%	$155.0105	$155.01	$155.00	$155.00
Purchase #6	$211.52	11.279%	$235.3773	$235.38	$235.40	$235.40
Purchase #7	$68.37	6.609%	$72.8886	$72.89	$72.90	$72.90
7 purchase totals =	$938.08		$1,016.0408	$1,016.04	$1,016.10	$1,016.10