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	$79.41	8.262%	$85.9709	$85.97	$85.95	$86.00
Purchase #2	$55.72	7.487%	$59.8918	$59.89	$59.90	$59.90
Purchase #3	$15.78	4.411%	$16.4761	$16.48	$16.50	$16.50
Purchase #4	$78.31	12.545%	$88.134	$88.13	$88.15	$88.10
Purchase #5	$242.56	11.859%	$271.3252	$271.33	$271.35	$271.30
Purchase #6	$37.68	3.242%	$38.9016	$38.90	$38.90	$38.90
Purchase #7	$64.73	5.667%	$68.3982	$68.40	$68.40	$68.40
7 purchase totals =	$574.19		$629.0978	$629.10	$629.15	$629.10