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	$64.56	10.222%	$71.1593	$71.16	$71.15	$71.20
Purchase #2	$211.38	13.177%	$239.2335	$239.23	$239.25	$239.20
Purchase #3	$9.83	3.764%	$10.2	$10.20	$10.20	$10.20
Purchase #4	$206.62	7.156%	$221.4057	$221.41	$221.40	$221.40
Purchase #5	$174.40	12.724%	$196.5907	$196.59	$196.60	$196.60
Purchase #6	$161.43	13.367%	$183.0083	$183.01	$183.00	$183.00
Purchase #7	$131.83	10.261%	$145.3571	$145.36	$145.35	$145.40
7 purchase totals =	$960.05		$1,066.9546	$1,066.96	$1,066.95	$1,067.00