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	$123.95	6.353%	$131.8245	$131.82	$131.80	$131.80
Purchase #2	$55.94	5.646%	$59.0984	$59.10	$59.10	$59.10
Purchase #3	$184.29	11.675%	$205.8059	$205.81	$205.80	$205.80
Purchase #4	$6.71	7.284%	$7.1988	$7.20	$7.20	$7.20
Purchase #5	$249.28	10.180%	$274.6567	$274.66	$274.65	$274.70
Purchase #6	$91.47	3.655%	$94.8132	$94.81	$94.80	$94.80
Purchase #7	$114.59	9.523%	$125.5024	$125.50	$125.50	$125.50
7 purchase totals =	$826.23		$898.8999	$898.90	$898.85	$898.90