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	$118.48	7.612%	$127.4987	$127.50	$127.50	$127.50
Purchase #2	$224.51	3.263%	$231.8358	$231.84	$231.85	$231.80
Purchase #3	$171.51	6.849%	$183.2567	$183.26	$183.25	$183.30
Purchase #4	$59.66	13.728%	$67.8501	$67.85	$67.85	$67.90
Purchase #5	$196.52	12.529%	$221.142	$221.14	$221.15	$221.10
Purchase #6	$117.89	8.425%	$127.8222	$127.82	$127.80	$127.80
Purchase #7	$166.68	8.746%	$181.2578	$181.26	$181.25	$181.30
7 purchase totals =	$1,055.25		$1,140.6633	$1,140.67	$1,140.65	$1,140.70