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	$162.70	7.639%	$175.1287	$175.13	$175.15	$175.10
Purchase #2	$112.86	9.391%	$123.4587	$123.46	$123.45	$123.50
Purchase #3	$133.67	5.281%	$140.7291	$140.73	$140.75	$140.70
Purchase #4	$40.93	12.106%	$45.885	$45.89	$45.90	$45.90
Purchase #5	$66.33	8.678%	$72.0861	$72.09	$72.10	$72.10
Purchase #6	$162.50	11.634%	$181.4053	$181.41	$181.40	$181.40
Purchase #7	$7.88	11.396%	$8.778	$8.78	$8.80	$8.80
7 purchase totals =	$686.87		$747.4709	$747.49	$747.55	$747.50