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	$47.44	13.623%	$53.9028	$53.90	$53.90	$53.90
Purchase #2	$11.98	8.556%	$13.005	$13.01	$13.00	$13.00
Purchase #3	$247.69	11.727%	$276.7366	$276.74	$276.75	$276.70
Purchase #4	$245.74	10.662%	$271.9408	$271.94	$271.95	$271.90
Purchase #5	$126.69	3.594%	$131.2432	$131.24	$131.25	$131.20
Purchase #6	$238.89	10.855%	$264.8215	$264.82	$264.80	$264.80
Purchase #7	$121.98	8.191%	$131.9714	$131.97	$131.95	$132.00
7 purchase totals =	$1,040.41		$1,143.6213	$1,143.62	$1,143.60	$1,143.50