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	$52.62	12.145%	$59.0107	$59.01	$59.00	$59.00
Purchase #2	$95.50	4.820%	$100.1031	$100.10	$100.10	$100.10
Purchase #3	$92.37	4.123%	$96.1784	$96.18	$96.20	$96.20
Purchase #4	$232.57	12.577%	$261.8203	$261.82	$261.80	$261.80
Purchase #5	$153.94	6.584%	$164.0754	$164.08	$164.10	$164.10
Purchase #6	$211.35	3.749%	$219.2735	$219.27	$219.25	$219.30
Purchase #7	$163.52	10.313%	$180.3838	$180.38	$180.40	$180.40
7 purchase totals =	$1,001.87		$1,080.8452	$1,080.84	$1,080.85	$1,080.90