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	$199.30	13.260%	$225.7272	$225.73	$225.75	$225.70
Purchase #2	$100.73	7.371%	$108.1548	$108.15	$108.15	$108.20
Purchase #3	$52.82	5.596%	$55.7758	$55.78	$55.80	$55.80
Purchase #4	$221.57	10.426%	$244.6709	$244.67	$244.65	$244.70
Purchase #5	$157.51	13.856%	$179.3346	$179.33	$179.35	$179.30
Purchase #6	$174.84	12.396%	$196.5132	$196.51	$196.50	$196.50
Purchase #7	$233.81	5.596%	$246.894	$246.89	$246.90	$246.90
7 purchase totals =	$1,140.58		$1,257.0705	$1,257.06	$1,257.10	$1,257.10