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	$116.99	3.208%	$120.743	$120.74	$120.75	$120.70
Purchase #2	$40.71	4.663%	$42.6083	$42.61	$42.60	$42.60
Purchase #3	$66.47	8.673%	$72.2349	$72.23	$72.25	$72.20
Purchase #4	$35.94	13.540%	$40.8063	$40.81	$40.80	$40.80
Purchase #5	$195.28	13.589%	$221.8166	$221.82	$221.80	$221.80
Purchase #6	$5.47	7.408%	$5.8752	$5.88	$5.90	$5.90
Purchase #7	$177.73	6.272%	$188.8772	$188.88	$188.90	$188.90
7 purchase totals =	$638.59		$692.9615	$692.97	$693.00	$692.90