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	$142.63	5.481%	$150.4476	$150.45	$150.45	$150.40
Purchase #2	$86.80	10.458%	$95.8775	$95.88	$95.90	$95.90
Purchase #3	$46.66	12.744%	$52.6064	$52.61	$52.60	$52.60
Purchase #4	$38.28	5.657%	$40.4455	$40.45	$40.45	$40.40
Purchase #5	$127.27	3.500%	$131.7245	$131.72	$131.70	$131.70
Purchase #6	$167.34	7.742%	$180.2955	$180.30	$180.30	$180.30
Purchase #7	$34.63	3.662%	$35.8982	$35.90	$35.90	$35.90
7 purchase totals =	$643.61		$687.2952	$687.31	$687.30	$687.20