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	$82.82	7.500%	$89.0315	$89.03	$89.05	$89.00
Purchase #2	$38.45	12.842%	$43.3877	$43.39	$43.40	$43.40
Purchase #3	$154.98	7.492%	$166.5911	$166.59	$166.60	$166.60
Purchase #4	$105.73	9.705%	$115.9911	$115.99	$116.00	$116.00
Purchase #5	$177.29	8.535%	$192.4217	$192.42	$192.40	$192.40
Purchase #6	$229.84	10.565%	$254.1226	$254.12	$254.10	$254.10
Purchase #7	$242.82	3.731%	$251.8796	$251.88	$251.90	$251.90
7 purchase totals =	$1,031.93		$1,113.4253	$1,113.42	$1,113.45	$1,113.40