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	$203.74	5.282%	$214.5015	$214.50	$214.50	$214.50
Purchase #2	$217.48	12.167%	$243.9408	$243.94	$243.95	$243.90
Purchase #3	$249.67	7.472%	$268.3253	$268.33	$268.35	$268.30
Purchase #4	$41.46	11.108%	$46.0654	$46.07	$46.05	$46.10
Purchase #5	$154.43	13.209%	$174.8287	$174.83	$174.85	$174.80
Purchase #6	$87.43	3.620%	$90.595	$90.60	$90.60	$90.60
Purchase #7	$109.51	7.730%	$117.9751	$117.98	$118.00	$118.00
7 purchase totals =	$1,063.72		$1,156.2318	$1,156.25	$1,156.30	$1,156.20