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	$139.97	13.517%	$158.8897	$158.89	$158.90	$158.90
Purchase #2	$230.86	13.388%	$261.7675	$261.77	$261.75	$261.80
Purchase #3	$111.25	7.295%	$119.3657	$119.37	$119.35	$119.40
Purchase #4	$38.75	12.592%	$43.6294	$43.63	$43.65	$43.60
Purchase #5	$238.34	10.759%	$263.983	$263.98	$264.00	$264.00
Purchase #6	$108.82	7.140%	$116.5897	$116.59	$116.60	$116.60
Purchase #7	$215.66	6.804%	$230.3335	$230.33	$230.35	$230.30
7 purchase totals =	$1,083.65		$1,194.5585	$1,194.56	$1,194.60	$1,194.60