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	$46.39	13.853%	$52.8164	$52.82	$52.80	$52.80
Purchase #2	$189.72	5.551%	$200.2514	$200.25	$200.25	$200.30
Purchase #3	$155.92	12.258%	$175.0327	$175.03	$175.05	$175.00
Purchase #4	$42.98	3.661%	$44.5535	$44.55	$44.55	$44.60
Purchase #5	$166.69	10.778%	$184.6558	$184.66	$184.65	$184.70
Purchase #6	$198.25	12.224%	$222.4841	$222.48	$222.50	$222.50
Purchase #7	$201.48	6.255%	$214.0826	$214.08	$214.10	$214.10
7 purchase totals =	$1,001.43		$1,093.8765	$1,093.87	$1,093.90	$1,094.00