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	$35.51	5.175%	$37.3476	$37.35	$37.35	$37.30
Purchase #2	$121.76	9.527%	$133.3601	$133.36	$133.35	$133.40
Purchase #3	$96.98	3.501%	$100.3753	$100.38	$100.40	$100.40
Purchase #4	$36.51	11.116%	$40.5685	$40.57	$40.55	$40.60
Purchase #5	$127.51	12.179%	$143.0394	$143.04	$143.05	$143.00
Purchase #6	$164.61	11.273%	$183.1665	$183.17	$183.15	$183.20
Purchase #7	$9.61	13.569%	$10.914	$10.91	$10.90	$10.90
7 purchase totals =	$592.49		$648.7714	$648.78	$648.75	$648.80