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	$163.95	13.193%	$185.5799	$185.58	$185.60	$185.60
Purchase #2	$207.31	7.107%	$222.0435	$222.04	$222.05	$222.00
Purchase #3	$114.50	4.212%	$119.3227	$119.32	$119.30	$119.30
Purchase #4	$106.30	11.827%	$118.8721	$118.87	$118.85	$118.90
Purchase #5	$131.25	12.625%	$147.8203	$147.82	$147.80	$147.80
Purchase #6	$172.72	5.287%	$181.8517	$181.85	$181.85	$181.90
Purchase #7	$60.66	6.503%	$64.6047	$64.60	$64.60	$64.60
7 purchase totals =	$956.69		$1,040.0949	$1,040.08	$1,040.05	$1,040.10