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	$76.92	6.767%	$82.1252	$82.13	$82.15	$82.10
Purchase #2	$89.59	12.622%	$100.898	$100.90	$100.90	$100.90
Purchase #3	$243.35	12.276%	$273.2236	$273.22	$273.20	$273.20
Purchase #4	$99.61	4.399%	$103.9918	$103.99	$104.00	$104.00
Purchase #5	$125.53	5.470%	$132.3965	$132.40	$132.40	$132.40
Purchase #6	$213.75	3.167%	$220.5195	$220.52	$220.50	$220.50
Purchase #7	$177.78	4.477%	$185.7392	$185.74	$185.75	$185.70
7 purchase totals =	$1,026.53		$1,098.8938	$1,098.90	$1,098.90	$1,098.80