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	$117.69	7.164%	$126.1213	$126.12	$126.10	$126.10
Purchase #2	$86.42	11.809%	$96.6253	$96.63	$96.65	$96.60
Purchase #3	$129.30	10.514%	$142.8946	$142.89	$142.90	$142.90
Purchase #4	$29.64	9.293%	$32.3944	$32.39	$32.40	$32.40
Purchase #5	$48.86	13.464%	$55.4385	$55.44	$55.45	$55.40
Purchase #6	$154.95	10.382%	$171.0369	$171.04	$171.05	$171.00
Purchase #7	$221.92	6.758%	$236.9174	$236.92	$236.90	$236.90
7 purchase totals =	$788.78		$861.4284	$861.43	$861.45	$861.30