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	$88.63	10.822%	$98.2215	$98.22	$98.20	$98.20
Purchase #2	$186.82	3.557%	$193.4652	$193.47	$193.45	$193.50
Purchase #3	$111.65	10.595%	$123.4793	$123.48	$123.50	$123.50
Purchase #4	$113.30	12.178%	$127.0977	$127.10	$127.10	$127.10
Purchase #5	$117.85	11.819%	$131.7787	$131.78	$131.80	$131.80
Purchase #6	$190.39	9.262%	$208.0239	$208.02	$208.00	$208.00
Purchase #7	$176.95	13.235%	$200.3693	$200.37	$200.35	$200.40
7 purchase totals =	$985.59		$1,082.4356	$1,082.44	$1,082.40	$1,082.50