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	$222.51	7.600%	$239.4208	$239.42	$239.40	$239.40
Purchase #2	$46.93	12.574%	$52.831	$52.83	$52.85	$52.80
Purchase #3	$25.90	7.345%	$27.8024	$27.80	$27.80	$27.80
Purchase #4	$112.41	9.794%	$123.4194	$123.42	$123.40	$123.40
Purchase #5	$178.66	12.298%	$200.6316	$200.63	$200.65	$200.60
Purchase #6	$149.36	5.854%	$158.1035	$158.10	$158.10	$158.10
Purchase #7	$109.55	3.449%	$113.3284	$113.33	$113.35	$113.30
7 purchase totals =	$845.32		$915.5371	$915.53	$915.55	$915.40