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	$83.71	8.174%	$90.5525	$90.55	$90.55	$90.60
Purchase #2	$19.69	8.795%	$21.4217	$21.42	$21.40	$21.40
Purchase #3	$206.54	13.626%	$234.6831	$234.68	$234.70	$234.70
Purchase #4	$63.70	4.507%	$66.571	$66.57	$66.55	$66.60
Purchase #5	$204.95	3.104%	$211.3116	$211.31	$211.30	$211.30
Purchase #6	$212.69	4.661%	$222.6035	$222.60	$222.60	$222.60
Purchase #7	$212.65	11.407%	$236.907	$236.91	$236.90	$236.90
7 purchase totals =	$1,003.93		$1,084.0504	$1,084.04	$1,084.00	$1,084.10