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	$156.92	6.451%	$167.0429	$167.04	$167.05	$167.00
Purchase #2	$249.29	12.576%	$280.6407	$280.64	$280.65	$280.60
Purchase #3	$78.29	8.684%	$85.0887	$85.09	$85.10	$85.10
Purchase #4	$19.36	6.593%	$20.6364	$20.64	$20.65	$20.60
Purchase #5	$114.28	3.529%	$118.3129	$118.31	$118.30	$118.30
Purchase #6	$219.95	5.694%	$232.474	$232.47	$232.45	$232.50
Purchase #7	$184.38	13.233%	$208.779	$208.78	$208.80	$208.80
7 purchase totals =	$1,022.47		$1,112.9746	$1,112.97	$1,113.00	$1,112.90