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	$54.38	13.456%	$61.6974	$61.70	$61.70	$61.70
Purchase #2	$231.69	10.381%	$255.7417	$255.74	$255.75	$255.70
Purchase #3	$186.28	5.632%	$196.7713	$196.77	$196.75	$196.80
Purchase #4	$143.58	9.519%	$157.2474	$157.25	$157.25	$157.20
Purchase #5	$82.46	7.587%	$88.7162	$88.72	$88.70	$88.70
Purchase #6	$71.75	9.855%	$78.821	$78.82	$78.80	$78.80
Purchase #7	$76.73	10.423%	$84.7276	$84.73	$84.75	$84.70
7 purchase totals =	$846.87		$923.7226	$923.73	$923.70	$923.60