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	$241.34	9.267%	$263.705	$263.71	$263.70	$263.70
Purchase #2	$67.81	4.524%	$70.8777	$70.88	$70.90	$70.90
Purchase #3	$69.75	3.640%	$72.2889	$72.29	$72.30	$72.30
Purchase #4	$123.89	6.465%	$131.8995	$131.90	$131.90	$131.90
Purchase #5	$67.48	5.480%	$71.1779	$71.18	$71.20	$71.20
Purchase #6	$10.55	12.127%	$11.8294	$11.83	$11.85	$11.80
Purchase #7	$159.93	8.850%	$174.0838	$174.08	$174.10	$174.10
7 purchase totals =	$740.75		$795.8622	$795.87	$795.95	$795.90