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	$156.96	4.874%	$164.6102	$164.61	$164.60	$164.60
Purchase #2	$250.56	9.588%	$274.5837	$274.58	$274.60	$274.60
Purchase #3	$244.26	12.124%	$273.8741	$273.87	$273.85	$273.90
Purchase #4	$16.41	10.329%	$18.105	$18.11	$18.10	$18.10
Purchase #5	$70.92	10.532%	$78.3893	$78.39	$78.40	$78.40
Purchase #6	$112.48	5.509%	$118.6765	$118.68	$118.70	$118.70
Purchase #7	$31.33	8.144%	$33.8815	$33.88	$33.90	$33.90
7 purchase totals =	$882.92		$962.1203	$962.12	$962.15	$962.20