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	$55.77	5.533%	$58.8558	$58.86	$58.85	$58.90
Purchase #2	$214.93	8.413%	$233.0121	$233.01	$233.00	$233.00
Purchase #3	$88.80	11.389%	$98.9134	$98.91	$98.90	$98.90
Purchase #4	$162.78	10.760%	$180.2951	$180.30	$180.30	$180.30
Purchase #5	$188.34	4.561%	$196.9302	$196.93	$196.95	$196.90
Purchase #6	$131.47	3.638%	$136.2529	$136.25	$136.25	$136.30
Purchase #7	$59.35	9.850%	$65.196	$65.20	$65.20	$65.20
7 purchase totals =	$901.44		$969.4555	$969.46	$969.45	$969.50