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	$204.82	4.742%	$214.5326	$214.53	$214.55	$214.50
Purchase #2	$187.89	11.469%	$209.4391	$209.44	$209.45	$209.40
Purchase #3	$94.80	8.627%	$102.9784	$102.98	$103.00	$103.00
Purchase #4	$155.51	10.818%	$172.3331	$172.33	$172.35	$172.30
Purchase #5	$192.37	3.567%	$199.2318	$199.23	$199.25	$199.20
Purchase #6	$36.84	11.136%	$40.9425	$40.94	$40.95	$40.90
Purchase #7	$43.35	5.472%	$45.7221	$45.72	$45.70	$45.70
7 purchase totals =	$915.58		$985.1796	$985.17	$985.25	$985.00