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	$160.32	13.334%	$181.6971	$181.70	$181.70	$181.70
Purchase #2	$248.83	7.639%	$267.8381	$267.84	$267.85	$267.80
Purchase #3	$55.31	13.612%	$62.8388	$62.84	$62.85	$62.80
Purchase #4	$83.34	8.627%	$90.5297	$90.53	$90.55	$90.50
Purchase #5	$70.78	7.670%	$76.2088	$76.21	$76.20	$76.20
Purchase #6	$220.57	3.858%	$229.0796	$229.08	$229.10	$229.10
Purchase #7	$198.46	12.614%	$223.4937	$223.49	$223.50	$223.50
7 purchase totals =	$1,037.61		$1,131.6858	$1,131.69	$1,131.75	$1,131.60