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	$210.80	10.682%	$233.3177	$233.32	$233.30	$233.30
Purchase #2	$125.80	12.300%	$141.2734	$141.27	$141.25	$141.30
Purchase #3	$153.66	7.331%	$164.9248	$164.92	$164.90	$164.90
Purchase #4	$77.42	10.706%	$85.7086	$85.71	$85.70	$85.70
Purchase #5	$33.30	12.823%	$37.5701	$37.57	$37.55	$37.60
Purchase #6	$13.38	11.441%	$14.9108	$14.91	$14.90	$14.90
Purchase #7	$79.94	3.555%	$82.7819	$82.78	$82.80	$82.80
7 purchase totals =	$694.30		$760.4873	$760.48	$760.40	$760.50