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	$138.84	9.645%	$152.2311	$152.23	$152.25	$152.20
Purchase #2	$108.32	3.289%	$111.8826	$111.88	$111.90	$111.90
Purchase #3	$7.82	13.366%	$8.8652	$8.87	$8.85	$8.90
Purchase #4	$50.53	9.384%	$55.2717	$55.27	$55.25	$55.30
Purchase #5	$152.54	11.621%	$170.2667	$170.27	$170.25	$170.30
Purchase #6	$105.36	11.481%	$117.4564	$117.46	$117.45	$117.50
Purchase #7	$144.50	5.833%	$152.9287	$152.93	$152.95	$152.90
7 purchase totals =	$707.91		$768.9024	$768.91	$768.90	$769.00