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	$81.82	5.665%	$86.4551	$86.46	$86.45	$86.50
Purchase #2	$92.73	8.357%	$100.4794	$100.48	$100.50	$100.50
Purchase #3	$165.49	7.143%	$177.311	$177.31	$177.30	$177.30
Purchase #4	$89.76	6.354%	$95.4634	$95.46	$95.45	$95.50
Purchase #5	$246.55	13.560%	$279.9822	$279.98	$280.00	$280.00
Purchase #6	$43.74	7.354%	$46.9566	$46.96	$46.95	$47.00
Purchase #7	$245.67	11.517%	$273.9638	$273.96	$273.95	$274.00
7 purchase totals =	$965.76		$1,060.6115	$1,060.61	$1,060.60	$1,060.80