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	$25.44	7.753%	$27.4124	$27.41	$27.40	$27.40
Purchase #2	$202.47	11.519%	$225.7925	$225.79	$225.80	$225.80
Purchase #3	$67.78	5.326%	$71.39	$71.39	$71.40	$71.40
Purchase #4	$112.98	6.675%	$120.5214	$120.52	$120.50	$120.50
Purchase #5	$62.72	12.520%	$70.5725	$70.57	$70.55	$70.60
Purchase #6	$106.45	5.468%	$112.2707	$112.27	$112.25	$112.30
Purchase #7	$121.37	10.307%	$133.8796	$133.88	$133.90	$133.90
7 purchase totals =	$699.21		$761.8391	$761.83	$761.80	$761.90