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	$144.81	7.242%	$155.2971	$155.30	$155.30	$155.30
Purchase #2	$66.75	8.694%	$72.5532	$72.55	$72.55	$72.60
Purchase #3	$85.40	5.768%	$90.3259	$90.33	$90.35	$90.30
Purchase #4	$93.29	7.686%	$100.4603	$100.46	$100.45	$100.50
Purchase #5	$192.75	8.368%	$208.8793	$208.88	$208.90	$208.90
Purchase #6	$95.56	7.689%	$102.9076	$102.91	$102.90	$102.90
Purchase #7	$151.37	5.243%	$159.3063	$159.31	$159.30	$159.30
7 purchase totals =	$829.93		$889.7297	$889.74	$889.75	$889.80