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	$123.53	7.245%	$132.4797	$132.48	$132.50	$132.50
Purchase #2	$100.37	8.828%	$109.2307	$109.23	$109.25	$109.20
Purchase #3	$6.28	12.747%	$7.0805	$7.08	$7.10	$7.10
Purchase #4	$190.46	13.867%	$216.8711	$216.87	$216.85	$216.90
Purchase #5	$225.64	12.411%	$253.6442	$253.64	$253.65	$253.60
Purchase #6	$125.30	12.828%	$141.3735	$141.37	$141.35	$141.40
Purchase #7	$57.54	12.682%	$64.8372	$64.84	$64.85	$64.80
7 purchase totals =	$829.12		$925.5169	$925.51	$925.55	$925.50