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	$41.61	12.448%	$46.7896	$46.79	$46.80	$46.80
Purchase #2	$205.45	8.292%	$222.4859	$222.49	$222.50	$222.50
Purchase #3	$205.52	5.132%	$216.0673	$216.07	$216.05	$216.10
Purchase #4	$210.37	9.236%	$229.7998	$229.80	$229.80	$229.80
Purchase #5	$92.60	13.417%	$105.0241	$105.02	$105.00	$105.00
Purchase #6	$250.42	12.261%	$281.124	$281.12	$281.10	$281.10
Purchase #7	$91.88	9.495%	$100.604	$100.60	$100.60	$100.60
7 purchase totals =	$1,097.85		$1,201.8947	$1,201.89	$1,201.85	$1,201.90