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	$94.90	5.640%	$100.2524	$100.25	$100.25	$100.30
Purchase #2	$27.59	13.686%	$31.366	$31.37	$31.35	$31.40
Purchase #3	$131.45	8.428%	$142.5286	$142.53	$142.55	$142.50
Purchase #4	$189.42	4.225%	$197.423	$197.42	$197.40	$197.40
Purchase #5	$227.97	12.514%	$256.4982	$256.50	$256.50	$256.50
Purchase #6	$94.56	6.813%	$101.0024	$101.00	$101.00	$101.00
Purchase #7	$249.82	3.288%	$258.0341	$258.03	$258.05	$258.00
7 purchase totals =	$1,015.71		$1,087.1047	$1,087.10	$1,087.10	$1,087.10