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	$12.91	10.676%	$14.2883	$14.29	$14.30	$14.30
Purchase #2	$92.33	3.810%	$95.8478	$95.85	$95.85	$95.80
Purchase #3	$56.96	3.742%	$59.0914	$59.09	$59.10	$59.10
Purchase #4	$78.46	12.424%	$88.2079	$88.21	$88.20	$88.20
Purchase #5	$86.31	13.265%	$97.759	$97.76	$97.75	$97.80
Purchase #6	$37.86	4.402%	$39.5266	$39.53	$39.55	$39.50
Purchase #7	$95.49	8.196%	$103.3164	$103.32	$103.30	$103.30
7 purchase totals =	$460.32		$498.0374	$498.05	$498.05	$498.00