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	$92.69	11.353%	$103.2131	$103.21	$103.20	$103.20
Purchase #2	$172.55	11.161%	$191.8083	$191.81	$191.80	$191.80
Purchase #3	$190.56	12.112%	$213.6406	$213.64	$213.65	$213.60
Purchase #4	$230.96	6.656%	$246.3327	$246.33	$246.35	$246.30
Purchase #5	$176.74	7.835%	$190.5876	$190.59	$190.60	$190.60
Purchase #6	$150.89	11.597%	$168.3887	$168.39	$168.40	$168.40
Purchase #7	$88.29	13.800%	$100.474	$100.47	$100.45	$100.50
7 purchase totals =	$1,102.68		$1,214.4450	$1,214.44	$1,214.45	$1,214.40