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	$109.36	5.791%	$115.693	$115.69	$115.70	$115.70
Purchase #2	$154.39	6.448%	$164.3451	$164.35	$164.35	$164.30
Purchase #3	$174.48	8.614%	$189.5097	$189.51	$189.50	$189.50
Purchase #4	$219.51	12.259%	$246.4197	$246.42	$246.40	$246.40
Purchase #5	$182.44	7.758%	$196.5937	$196.59	$196.60	$196.60
Purchase #6	$237.75	6.606%	$253.4558	$253.46	$253.45	$253.50
Purchase #7	$150.83	11.638%	$168.3836	$168.38	$168.40	$168.40
7 purchase totals =	$1,228.76		$1,334.4006	$1,334.40	$1,334.40	$1,334.40