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	$73.84	12.300%	$82.9223	$82.92	$82.90	$82.90
Purchase #2	$12.43	6.562%	$13.2457	$13.25	$13.25	$13.20
Purchase #3	$142.67	8.306%	$154.5202	$154.52	$154.50	$154.50
Purchase #4	$130.95	6.819%	$139.8795	$139.88	$139.90	$139.90
Purchase #5	$176.80	6.724%	$188.688	$188.69	$188.70	$188.70
Purchase #6	$103.86	7.517%	$111.6672	$111.67	$111.65	$111.70
Purchase #7	$228.66	13.744%	$260.087	$260.09	$260.10	$260.10
7 purchase totals =	$869.21		$951.0099	$951.02	$951.00	$951.00