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	$10.64	11.463%	$11.8597	$11.86	$11.85	$11.90
Purchase #2	$241.95	11.547%	$269.888	$269.89	$269.90	$269.90
Purchase #3	$142.66	8.252%	$154.4323	$154.43	$154.45	$154.40
Purchase #4	$185.73	6.874%	$198.4971	$198.50	$198.50	$198.50
Purchase #5	$174.56	10.473%	$192.8417	$192.84	$192.85	$192.80
Purchase #6	$109.62	9.593%	$120.1358	$120.14	$120.15	$120.10
Purchase #7	$151.59	9.807%	$166.4564	$166.46	$166.45	$166.50
7 purchase totals =	$1,016.75		$1,114.1110	$1,114.12	$1,114.15	$1,114.10