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	$192.29	3.340%	$198.7125	$198.71	$198.70	$198.70
Purchase #2	$51.65	3.480%	$53.4474	$53.45	$53.45	$53.40
Purchase #3	$51.50	6.572%	$54.8846	$54.88	$54.90	$54.90
Purchase #4	$34.46	12.841%	$38.885	$38.89	$38.90	$38.90
Purchase #5	$12.36	8.458%	$13.4054	$13.41	$13.40	$13.40
Purchase #6	$46.86	7.408%	$50.3314	$50.33	$50.35	$50.30
Purchase #7	$52.47	9.807%	$57.6157	$57.62	$57.60	$57.60
7 purchase totals =	$441.59		$467.2820	$467.29	$467.30	$467.20