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	$150.72	11.729%	$168.3979	$168.40	$168.40	$168.40
Purchase #2	$47.58	11.322%	$52.967	$52.97	$52.95	$53.00
Purchase #3	$67.90	6.638%	$72.4072	$72.41	$72.40	$72.40
Purchase #4	$90.73	5.482%	$95.7038	$95.70	$95.70	$95.70
Purchase #5	$217.75	8.564%	$236.3981	$236.40	$236.40	$236.40
Purchase #6	$83.48	3.639%	$86.5178	$86.52	$86.50	$86.50
Purchase #7	$24.34	3.638%	$25.2255	$25.23	$25.25	$25.20
7 purchase totals =	$682.50		$737.6173	$737.63	$737.60	$737.60