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	$121.93	4.697%	$127.6571	$127.66	$127.65	$127.70
Purchase #2	$238.38	7.706%	$256.7496	$256.75	$256.75	$256.70
Purchase #3	$237.94	13.745%	$270.6449	$270.64	$270.65	$270.60
Purchase #4	$67.93	5.142%	$71.423	$71.42	$71.40	$71.40
Purchase #5	$139.46	3.687%	$144.6019	$144.60	$144.60	$144.60
Purchase #6	$196.69	3.491%	$203.5564	$203.56	$203.55	$203.60
Purchase #7	$237.55	12.697%	$267.7117	$267.71	$267.70	$267.70
7 purchase totals =	$1,239.88		$1,342.3446	$1,342.34	$1,342.30	$1,342.30