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	$229.57	11.446%	$255.8466	$255.85	$255.85	$255.80
Purchase #2	$174.94	13.262%	$198.1405	$198.14	$198.15	$198.10
Purchase #3	$62.74	5.423%	$66.1424	$66.14	$66.15	$66.10
Purchase #4	$155.38	12.834%	$175.3215	$175.32	$175.30	$175.30
Purchase #5	$242.57	12.489%	$272.8646	$272.86	$272.85	$272.90
Purchase #6	$38.84	11.736%	$43.3983	$43.40	$43.40	$43.40
Purchase #7	$77.98	3.639%	$80.8177	$80.82	$80.80	$80.80
7 purchase totals =	$982.02		$1,092.5316	$1,092.53	$1,092.50	$1,092.40