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	$206.42	7.763%	$222.4444	$222.44	$222.45	$222.40
Purchase #2	$54.86	12.574%	$61.7581	$61.76	$61.75	$61.80
Purchase #3	$38.96	3.742%	$40.4179	$40.42	$40.40	$40.40
Purchase #4	$176.97	3.201%	$182.6348	$182.63	$182.65	$182.60
Purchase #5	$153.84	5.413%	$162.1674	$162.17	$162.15	$162.20
Purchase #6	$196.85	11.529%	$219.5448	$219.54	$219.55	$219.50
Purchase #7	$53.95	6.371%	$57.3872	$57.39	$57.40	$57.40
7 purchase totals =	$881.85		$946.3546	$946.35	$946.35	$946.30