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	$107.31	8.738%	$116.6867	$116.69	$116.70	$116.70
Purchase #2	$171.48	5.767%	$181.3693	$181.37	$181.35	$181.40
Purchase #3	$249.32	8.214%	$269.7991	$269.80	$269.80	$269.80
Purchase #4	$157.28	4.617%	$164.5416	$164.54	$164.55	$164.50
Purchase #5	$85.96	6.380%	$91.4442	$91.44	$91.45	$91.40
Purchase #6	$237.87	3.631%	$246.5071	$246.51	$246.50	$246.50
Purchase #7	$58.54	5.134%	$61.5454	$61.55	$61.55	$61.50
7 purchase totals =	$1,067.76		$1,131.8934	$1,131.90	$1,131.90	$1,131.80