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	$144.56	13.859%	$164.5946	$164.59	$164.60	$164.60
Purchase #2	$46.41	11.376%	$51.6896	$51.69	$51.70	$51.70
Purchase #3	$125.74	4.830%	$131.8132	$131.81	$131.80	$131.80
Purchase #4	$186.87	5.627%	$197.3852	$197.39	$197.40	$197.40
Purchase #5	$200.94	11.432%	$223.9115	$223.91	$223.90	$223.90
Purchase #6	$226.93	12.351%	$254.9581	$254.96	$254.95	$255.00
Purchase #7	$86.92	4.265%	$90.6271	$90.63	$90.65	$90.60
7 purchase totals =	$1,018.37		$1,114.9793	$1,114.98	$1,115.00	$1,115.00