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	$176.64	13.698%	$200.8361	$200.84	$200.85	$200.80
Purchase #2	$16.78	8.375%	$18.1853	$18.19	$18.20	$18.20
Purchase #3	$39.87	8.761%	$43.363	$43.36	$43.35	$43.40
Purchase #4	$216.95	5.822%	$229.5808	$229.58	$229.60	$229.60
Purchase #5	$111.49	6.183%	$118.3834	$118.38	$118.40	$118.40
Purchase #6	$243.59	12.683%	$274.4845	$274.48	$274.50	$274.50
Purchase #7	$108.98	3.285%	$112.56	$112.56	$112.55	$112.60
7 purchase totals =	$914.30		$997.3931	$997.39	$997.45	$997.50