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	$131.70	10.757%	$145.867	$145.87	$145.85	$145.90
Purchase #2	$213.54	12.635%	$240.5208	$240.52	$240.50	$240.50
Purchase #3	$168.50	4.244%	$175.6511	$175.65	$175.65	$175.70
Purchase #4	$38.26	7.470%	$41.118	$41.12	$41.10	$41.10
Purchase #5	$200.74	8.604%	$218.0117	$218.01	$218.00	$218.00
Purchase #6	$90.82	8.861%	$98.8676	$98.87	$98.85	$98.90
Purchase #7	$96.65	13.667%	$109.8592	$109.86	$109.85	$109.90
7 purchase totals =	$940.21		$1,029.8954	$1,029.90	$1,029.80	$1,030.00