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	$126.53	7.822%	$136.4272	$136.43	$136.45	$136.40
Purchase #2	$17.53	7.809%	$18.8989	$18.90	$18.90	$18.90
Purchase #3	$119.45	6.289%	$126.9622	$126.96	$126.95	$127.00
Purchase #4	$78.46	9.772%	$86.1271	$86.13	$86.15	$86.10
Purchase #5	$228.45	13.167%	$258.53	$258.53	$258.55	$258.50
Purchase #6	$199.28	5.182%	$209.6067	$209.61	$209.60	$209.60
Purchase #7	$91.78	9.185%	$100.21	$100.21	$100.20	$100.20
7 purchase totals =	$861.48		$936.7621	$936.77	$936.80	$936.70