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	$75.38	7.357%	$80.9257	$80.93	$80.95	$80.90
Purchase #2	$199.72	9.143%	$217.9804	$217.98	$218.00	$218.00
Purchase #3	$227.30	9.675%	$249.2913	$249.29	$249.30	$249.30
Purchase #4	$57.88	3.161%	$59.7096	$59.71	$59.70	$59.70
Purchase #5	$141.86	11.102%	$157.6093	$157.61	$157.60	$157.60
Purchase #6	$48.81	6.290%	$51.8801	$51.88	$51.90	$51.90
Purchase #7	$178.56	7.205%	$191.4252	$191.43	$191.45	$191.40
7 purchase totals =	$929.51		$1,008.8216	$1,008.83	$1,008.90	$1,008.80