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	$71.75	9.867%	$78.8296	$78.83	$78.85	$78.80
Purchase #2	$90.78	6.790%	$96.944	$96.94	$96.95	$96.90
Purchase #3	$65.98	5.721%	$69.7547	$69.75	$69.75	$69.80
Purchase #4	$236.31	4.357%	$246.606	$246.61	$246.60	$246.60
Purchase #5	$89.48	7.309%	$96.0201	$96.02	$96.00	$96.00
Purchase #6	$108.83	7.153%	$116.6146	$116.61	$116.60	$116.60
Purchase #7	$10.93	7.785%	$11.7809	$11.78	$11.80	$11.80
7 purchase totals =	$674.06		$716.5499	$716.54	$716.55	$716.50