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	$225.29	13.199%	$255.026	$255.03	$255.05	$255.00
Purchase #2	$66.86	6.312%	$71.0802	$71.08	$71.10	$71.10
Purchase #3	$211.45	13.292%	$239.5559	$239.56	$239.55	$239.60
Purchase #4	$244.91	5.846%	$259.2274	$259.23	$259.25	$259.20
Purchase #5	$105.34	3.407%	$108.9289	$108.93	$108.95	$108.90
Purchase #6	$7.56	4.570%	$7.9055	$7.91	$7.90	$7.90
Purchase #7	$111.85	4.127%	$116.466	$116.47	$116.45	$116.50
7 purchase totals =	$973.26		$1,058.1899	$1,058.21	$1,058.25	$1,058.20