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	$87.97	13.191%	$99.5741	$99.57	$99.55	$99.60
Purchase #2	$196.35	10.602%	$217.167	$217.17	$217.15	$217.20
Purchase #3	$91.58	7.181%	$98.1564	$98.16	$98.15	$98.20
Purchase #4	$179.70	9.848%	$197.3969	$197.40	$197.40	$197.40
Purchase #5	$27.87	12.848%	$31.4507	$31.45	$31.45	$31.50
Purchase #6	$201.90	12.163%	$226.4571	$226.46	$226.45	$226.50
Purchase #7	$179.61	3.331%	$185.5928	$185.59	$185.60	$185.60
7 purchase totals =	$964.98		$1,055.7950	$1,055.80	$1,055.75	$1,056.00