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	$247.91	4.655%	$259.4502	$259.45	$259.45	$259.50
Purchase #2	$35.35	6.840%	$37.7679	$37.77	$37.75	$37.80
Purchase #3	$118.98	6.583%	$126.8125	$126.81	$126.80	$126.80
Purchase #4	$99.78	6.872%	$106.6369	$106.64	$106.65	$106.60
Purchase #5	$233.66	13.850%	$266.0219	$266.02	$266.00	$266.00
Purchase #6	$144.36	12.740%	$162.7515	$162.75	$162.75	$162.80
Purchase #7	$90.70	9.682%	$99.4816	$99.48	$99.50	$99.50
7 purchase totals =	$970.74		$1,058.9225	$1,058.92	$1,058.90	$1,059.00