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	$233.47	4.694%	$244.4291	$244.43	$244.45	$244.40
Purchase #2	$32.86	12.248%	$36.8847	$36.88	$36.90	$36.90
Purchase #3	$179.45	10.392%	$198.0984	$198.10	$198.10	$198.10
Purchase #4	$98.59	4.409%	$102.9368	$102.94	$102.95	$102.90
Purchase #5	$75.34	9.596%	$82.5696	$82.57	$82.55	$82.60
Purchase #6	$113.91	8.725%	$123.8486	$123.85	$123.85	$123.80
Purchase #7	$224.61	12.661%	$253.0479	$253.05	$253.05	$253.00
7 purchase totals =	$958.23		$1,041.8151	$1,041.82	$1,041.85	$1,041.70