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	$131.53	10.493%	$145.3314	$145.33	$145.35	$145.30
Purchase #2	$142.33	5.822%	$150.6165	$150.62	$150.60	$150.60
Purchase #3	$78.93	11.281%	$87.8341	$87.83	$87.85	$87.80
Purchase #4	$96.44	13.553%	$109.5105	$109.51	$109.50	$109.50
Purchase #5	$217.50	8.577%	$236.155	$236.16	$236.15	$236.20
Purchase #6	$177.48	10.771%	$196.5964	$196.60	$196.60	$196.60
Purchase #7	$123.58	6.580%	$131.7116	$131.71	$131.70	$131.70
7 purchase totals =	$967.79		$1,057.7555	$1,057.76	$1,057.75	$1,057.70