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	$53.37	11.708%	$59.6186	$59.62	$59.60	$59.60
Purchase #2	$98.93	3.203%	$102.0987	$102.10	$102.10	$102.10
Purchase #3	$82.84	9.728%	$90.8987	$90.90	$90.90	$90.90
Purchase #4	$154.97	7.225%	$166.1666	$166.17	$166.15	$166.20
Purchase #5	$185.56	3.778%	$192.5705	$192.57	$192.55	$192.60
Purchase #6	$202.97	4.724%	$212.5583	$212.56	$212.55	$212.60
Purchase #7	$48.29	12.313%	$54.2359	$54.24	$54.25	$54.20
7 purchase totals =	$826.93		$878.1473	$878.16	$878.10	$878.20