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	$24.36	9.687%	$26.7198	$26.72	$26.70	$26.70
Purchase #2	$238.90	3.682%	$247.6963	$247.70	$247.70	$247.70
Purchase #3	$100.54	3.461%	$104.0197	$104.02	$104.00	$104.00
Purchase #4	$45.50	7.393%	$48.8638	$48.86	$48.85	$48.90
Purchase #5	$54.30	9.547%	$59.484	$59.48	$59.50	$59.50
Purchase #6	$238.80	7.104%	$255.7644	$255.76	$255.75	$255.80
Purchase #7	$50.98	3.730%	$52.8816	$52.88	$52.90	$52.90
7 purchase totals =	$753.38		$795.4296	$795.42	$795.40	$795.50