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	$152.33	7.752%	$164.1386	$164.14	$164.15	$164.10
Purchase #2	$166.59	12.658%	$187.677	$187.68	$187.70	$187.70
Purchase #3	$222.99	11.508%	$248.6517	$248.65	$248.65	$248.70
Purchase #4	$79.56	3.417%	$82.2786	$82.28	$82.30	$82.30
Purchase #5	$141.95	8.786%	$154.4217	$154.42	$154.40	$154.40
Purchase #6	$224.82	12.153%	$252.1424	$252.14	$252.15	$252.10
Purchase #7	$31.53	7.496%	$33.8935	$33.89	$33.90	$33.90
7 purchase totals =	$1,019.77		$1,123.2035	$1,123.20	$1,123.25	$1,123.20