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	$186.30	13.702%	$211.8268	$211.83	$211.85	$211.80
Purchase #2	$246.34	8.291%	$266.764	$266.76	$266.75	$266.80
Purchase #3	$165.93	3.599%	$171.9018	$171.90	$171.90	$171.90
Purchase #4	$241.71	12.159%	$271.0995	$271.10	$271.10	$271.10
Purchase #5	$61.25	10.105%	$67.4393	$67.44	$67.45	$67.40
Purchase #6	$181.71	13.157%	$205.6176	$205.62	$205.60	$205.60
Purchase #7	$86.39	3.680%	$89.5692	$89.57	$89.55	$89.60
7 purchase totals =	$1,169.63		$1,284.2182	$1,284.22	$1,284.20	$1,284.20