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	$5.67	4.795%	$5.9419	$5.94	$5.95	$5.90
Purchase #2	$70.98	10.444%	$78.3932	$78.39	$78.40	$78.40
Purchase #3	$7.53	6.579%	$8.0254	$8.03	$8.05	$8.00
Purchase #4	$131.80	6.506%	$140.3749	$140.37	$140.35	$140.40
Purchase #5	$36.86	4.464%	$38.5054	$38.51	$38.50	$38.50
Purchase #6	$41.39	5.170%	$43.5299	$43.53	$43.55	$43.50
Purchase #7	$158.82	6.340%	$168.8892	$168.89	$168.90	$168.90
7 purchase totals =	$453.05		$483.6599	$483.66	$483.70	$483.60