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	$55.78	9.614%	$61.1427	$61.14	$61.15	$61.10
Purchase #2	$113.40	8.761%	$123.335	$123.34	$123.35	$123.30
Purchase #3	$163.94	5.480%	$172.9239	$172.92	$172.90	$172.90
Purchase #4	$74.81	4.767%	$78.3762	$78.38	$78.40	$78.40
Purchase #5	$221.53	3.674%	$229.669	$229.67	$229.65	$229.70
Purchase #6	$166.90	12.575%	$187.8877	$187.89	$187.90	$187.90
Purchase #7	$133.68	7.629%	$143.8784	$143.88	$143.90	$143.90
7 purchase totals =	$930.04		$997.2129	$997.22	$997.25	$997.20