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	$30.31	8.806%	$32.9791	$32.98	$33.00	$33.00
Purchase #2	$85.84	12.155%	$96.2739	$96.27	$96.25	$96.30
Purchase #3	$41.51	9.505%	$45.4555	$45.46	$45.45	$45.50
Purchase #4	$70.40	3.606%	$72.9386	$72.94	$72.95	$72.90
Purchase #5	$185.39	12.587%	$208.725	$208.73	$208.75	$208.70
Purchase #6	$231.55	7.567%	$249.0714	$249.07	$249.05	$249.10
Purchase #7	$237.81	9.305%	$259.9382	$259.94	$259.95	$259.90
7 purchase totals =	$882.81		$965.3817	$965.39	$965.40	$965.40