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	$69.47	4.284%	$72.4461	$72.45	$72.45	$72.40
Purchase #2	$164.71	12.284%	$184.943	$184.94	$184.95	$184.90
Purchase #3	$24.83	5.539%	$26.2053	$26.21	$26.20	$26.20
Purchase #4	$201.43	6.296%	$214.112	$214.11	$214.10	$214.10
Purchase #5	$180.28	6.108%	$191.2915	$191.29	$191.30	$191.30
Purchase #6	$82.50	10.178%	$90.8969	$90.90	$90.90	$90.90
Purchase #7	$179.46	10.863%	$198.9547	$198.95	$198.95	$199.00
7 purchase totals =	$902.68		$978.8495	$978.85	$978.85	$978.80