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	$92.29	10.785%	$102.2435	$102.24	$102.25	$102.20
Purchase #2	$184.95	7.346%	$198.5364	$198.54	$198.55	$198.50
Purchase #3	$70.65	4.605%	$73.9034	$73.90	$73.90	$73.90
Purchase #4	$206.79	4.227%	$215.531	$215.53	$215.55	$215.50
Purchase #5	$55.41	7.477%	$59.553	$59.55	$59.55	$59.60
Purchase #6	$54.52	4.229%	$56.8257	$56.83	$56.85	$56.80
Purchase #7	$106.96	11.701%	$119.4754	$119.48	$119.50	$119.50
7 purchase totals =	$771.57		$826.0684	$826.07	$826.15	$826.00