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	$175.86	9.588%	$192.7215	$192.72	$192.70	$192.70
Purchase #2	$231.53	3.175%	$238.8811	$238.88	$238.90	$238.90
Purchase #3	$138.53	8.869%	$150.8162	$150.82	$150.80	$150.80
Purchase #4	$48.43	10.214%	$53.3766	$53.38	$53.40	$53.40
Purchase #5	$115.34	11.119%	$128.1647	$128.16	$128.15	$128.20
Purchase #6	$198.26	8.557%	$215.2251	$215.23	$215.25	$215.20
Purchase #7	$164.96	13.594%	$187.3847	$187.38	$187.40	$187.40
7 purchase totals =	$1,072.91		$1,166.5699	$1,166.57	$1,166.60	$1,166.60