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	$208.32	9.112%	$227.3021	$227.30	$227.30	$227.30
Purchase #2	$103.78	5.462%	$109.4485	$109.45	$109.45	$109.40
Purchase #3	$87.35	3.240%	$90.1801	$90.18	$90.20	$90.20
Purchase #4	$180.47	13.299%	$204.4707	$204.47	$204.45	$204.50
Purchase #5	$201.69	5.801%	$213.39	$213.39	$213.40	$213.40
Purchase #6	$198.35	6.573%	$211.3875	$211.39	$211.40	$211.40
Purchase #7	$32.47	7.167%	$34.7971	$34.80	$34.80	$34.80
7 purchase totals =	$1,012.43		$1,090.9760	$1,090.98	$1,091.00	$1,091.00