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	$192.80	3.220%	$199.0082	$199.01	$199.00	$199.00
Purchase #2	$112.69	13.592%	$128.0068	$128.01	$128.00	$128.00
Purchase #3	$43.69	8.162%	$47.256	$47.26	$47.25	$47.30
Purchase #4	$36.65	5.339%	$38.6067	$38.61	$38.60	$38.60
Purchase #5	$21.32	13.689%	$24.2385	$24.24	$24.25	$24.20
Purchase #6	$145.86	10.800%	$161.6129	$161.61	$161.60	$161.60
Purchase #7	$96.29	3.149%	$99.3222	$99.32	$99.30	$99.30
7 purchase totals =	$649.30		$698.0513	$698.06	$698.00	$698.00