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	$124.61	11.754%	$139.2567	$139.26	$139.25	$139.30
Purchase #2	$225.87	5.387%	$238.0376	$238.04	$238.05	$238.00
Purchase #3	$176.34	3.445%	$182.4149	$182.41	$182.40	$182.40
Purchase #4	$82.68	8.167%	$89.4325	$89.43	$89.45	$89.40
Purchase #5	$136.85	4.221%	$142.6264	$142.63	$142.65	$142.60
Purchase #6	$91.38	7.356%	$98.1019	$98.10	$98.10	$98.10
Purchase #7	$157.96	13.601%	$179.4441	$179.44	$179.45	$179.40
7 purchase totals =	$995.69		$1,069.3141	$1,069.31	$1,069.35	$1,069.20