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	$187.41	4.760%	$196.3307	$196.33	$196.35	$196.30
Purchase #2	$179.92	3.162%	$185.6091	$185.61	$185.60	$185.60
Purchase #3	$80.59	9.284%	$88.072	$88.07	$88.05	$88.10
Purchase #4	$205.95	13.589%	$233.9365	$233.94	$233.95	$233.90
Purchase #5	$50.54	9.508%	$55.3453	$55.35	$55.35	$55.30
Purchase #6	$104.86	5.480%	$110.6063	$110.61	$110.60	$110.60
Purchase #7	$81.64	6.469%	$86.9213	$86.92	$86.90	$86.90
7 purchase totals =	$890.91		$956.8212	$956.83	$956.80	$956.70