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	$126.40	11.693%	$141.18	$141.18	$141.20	$141.20
Purchase #2	$249.44	11.576%	$278.3152	$278.32	$278.30	$278.30
Purchase #3	$187.77	3.822%	$194.9466	$194.95	$194.95	$194.90
Purchase #4	$37.51	12.674%	$42.264	$42.26	$42.25	$42.30
Purchase #5	$44.28	6.850%	$47.3132	$47.31	$47.30	$47.30
Purchase #6	$227.63	12.797%	$256.7598	$256.76	$256.75	$256.80
Purchase #7	$191.38	3.522%	$198.1204	$198.12	$198.10	$198.10
7 purchase totals =	$1,064.41		$1,158.8992	$1,158.90	$1,158.85	$1,158.90