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	$38.83	11.610%	$43.3382	$43.34	$43.35	$43.30
Purchase #2	$89.57	6.179%	$95.1045	$95.10	$95.10	$95.10
Purchase #3	$63.30	12.561%	$71.2511	$71.25	$71.25	$71.30
Purchase #4	$208.92	8.139%	$225.924	$225.92	$225.90	$225.90
Purchase #5	$90.72	8.299%	$98.2489	$98.25	$98.25	$98.20
Purchase #6	$122.72	10.716%	$135.8707	$135.87	$135.85	$135.90
Purchase #7	$243.25	8.427%	$263.7487	$263.75	$263.75	$263.70
7 purchase totals =	$857.31		$933.4861	$933.48	$933.45	$933.40