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	$10.48	4.304%	$10.9311	$10.93	$10.95	$10.90
Purchase #2	$217.82	11.567%	$243.0152	$243.02	$243.00	$243.00
Purchase #3	$212.37	5.367%	$223.7679	$223.77	$223.75	$223.80
Purchase #4	$114.80	4.542%	$120.0142	$120.01	$120.00	$120.00
Purchase #5	$155.81	7.767%	$167.9118	$167.91	$167.90	$167.90
Purchase #6	$52.70	13.724%	$59.9325	$59.93	$59.95	$59.90
Purchase #7	$212.92	13.226%	$241.0808	$241.08	$241.10	$241.10
7 purchase totals =	$976.90		$1,066.6535	$1,066.65	$1,066.65	$1,066.60