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	$123.65	6.831%	$132.0965	$132.10	$132.10	$132.10
Purchase #2	$237.89	10.503%	$262.8756	$262.88	$262.90	$262.90
Purchase #3	$76.48	6.345%	$81.3327	$81.33	$81.35	$81.30
Purchase #4	$137.29	10.681%	$151.9539	$151.95	$151.95	$152.00
Purchase #5	$87.30	6.646%	$93.102	$93.10	$93.10	$93.10
Purchase #6	$100.90	8.339%	$109.3141	$109.31	$109.30	$109.30
Purchase #7	$105.99	13.162%	$119.9404	$119.94	$119.95	$119.90
7 purchase totals =	$869.50		$950.6152	$950.61	$950.65	$950.60