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	$119.49	9.773%	$131.1678	$131.17	$131.15	$131.20
Purchase #2	$227.96	6.648%	$243.1148	$243.11	$243.10	$243.10
Purchase #3	$14.45	12.480%	$16.2534	$16.25	$16.25	$16.30
Purchase #4	$157.84	7.109%	$169.0608	$169.06	$169.05	$169.10
Purchase #5	$109.86	7.394%	$117.983	$117.98	$118.00	$118.00
Purchase #6	$148.29	12.349%	$166.6023	$166.60	$166.60	$166.60
Purchase #7	$89.82	9.215%	$98.0969	$98.10	$98.10	$98.10
7 purchase totals =	$867.71		$942.2790	$942.27	$942.25	$942.40