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	$229.60	11.750%	$256.578	$256.58	$256.60	$256.60
Purchase #2	$6.65	13.827%	$7.5695	$7.57	$7.55	$7.60
Purchase #3	$37.90	13.443%	$42.9949	$42.99	$43.00	$43.00
Purchase #4	$83.65	3.271%	$86.3862	$86.39	$86.40	$86.40
Purchase #5	$174.44	12.654%	$196.5136	$196.51	$196.50	$196.50
Purchase #6	$219.40	8.188%	$237.3645	$237.36	$237.35	$237.40
Purchase #7	$63.34	6.377%	$67.3792	$67.38	$67.40	$67.40
7 purchase totals =	$814.98		$894.7859	$894.78	$894.80	$894.90