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	$43.92	3.690%	$45.5406	$45.54	$45.55	$45.50
Purchase #2	$172.42	5.278%	$181.5203	$181.52	$181.50	$181.50
Purchase #3	$67.56	7.329%	$72.5115	$72.51	$72.50	$72.50
Purchase #4	$177.32	3.421%	$183.3861	$183.39	$183.40	$183.40
Purchase #5	$148.91	8.382%	$161.3916	$161.39	$161.40	$161.40
Purchase #6	$176.89	9.688%	$194.0271	$194.03	$194.05	$194.00
Purchase #7	$220.36	6.370%	$234.3969	$234.40	$234.40	$234.40
7 purchase totals =	$1,007.38		$1,072.7741	$1,072.78	$1,072.80	$1,072.70