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	$177.91	11.336%	$198.0779	$198.08	$198.10	$198.10
Purchase #2	$73.61	7.230%	$78.932	$78.93	$78.95	$78.90
Purchase #3	$41.83	13.484%	$47.4704	$47.47	$47.45	$47.50
Purchase #4	$140.79	7.572%	$151.4506	$151.45	$151.45	$151.50
Purchase #5	$90.58	12.871%	$102.2386	$102.24	$102.25	$102.20
Purchase #6	$127.51	3.829%	$132.3924	$132.39	$132.40	$132.40
Purchase #7	$19.32	9.459%	$21.1475	$21.15	$21.15	$21.10
7 purchase totals =	$671.55		$731.7094	$731.71	$731.75	$731.70