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	$109.57	12.305%	$123.0526	$123.05	$123.05	$123.10
Purchase #2	$209.95	13.303%	$237.8796	$237.88	$237.90	$237.90
Purchase #3	$166.33	13.344%	$188.5251	$188.53	$188.55	$188.50
Purchase #4	$157.25	10.210%	$173.3052	$173.31	$173.30	$173.30
Purchase #5	$206.31	7.767%	$222.3341	$222.33	$222.35	$222.30
Purchase #6	$126.99	5.379%	$133.8208	$133.82	$133.80	$133.80
Purchase #7	$97.50	8.628%	$105.9123	$105.91	$105.90	$105.90
7 purchase totals =	$1,073.90		$1,184.8297	$1,184.83	$1,184.85	$1,184.80