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	$174.27	10.300%	$192.2198	$192.22	$192.20	$192.20
Purchase #2	$214.88	11.832%	$240.3046	$240.30	$240.30	$240.30
Purchase #3	$122.29	5.405%	$128.8998	$128.90	$128.90	$128.90
Purchase #4	$232.65	9.838%	$255.5381	$255.54	$255.55	$255.50
Purchase #5	$38.97	5.269%	$41.0233	$41.02	$41.00	$41.00
Purchase #6	$126.55	8.785%	$137.6674	$137.67	$137.65	$137.70
Purchase #7	$52.86	4.844%	$55.4205	$55.42	$55.40	$55.40
7 purchase totals =	$962.47		$1,051.0735	$1,051.07	$1,051.00	$1,051.00