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	$215.77	12.525%	$242.7952	$242.80	$242.80	$242.80
Purchase #2	$135.33	4.556%	$141.4956	$141.50	$141.50	$141.50
Purchase #3	$198.92	12.397%	$223.5801	$223.58	$223.60	$223.60
Purchase #4	$49.33	12.731%	$55.6102	$55.61	$55.60	$55.60
Purchase #5	$200.49	12.225%	$224.9999	$225.00	$225.00	$225.00
Purchase #6	$53.90	4.587%	$56.3724	$56.37	$56.35	$56.40
Purchase #7	$78.37	9.597%	$85.8912	$85.89	$85.90	$85.90
7 purchase totals =	$932.11		$1,030.7446	$1,030.75	$1,030.75	$1,030.80