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	$147.63	13.341%	$167.3253	$167.33	$167.35	$167.30
Purchase #2	$67.68	10.851%	$75.024	$75.02	$75.00	$75.00
Purchase #3	$44.31	9.514%	$48.5257	$48.53	$48.55	$48.50
Purchase #4	$111.47	10.369%	$123.0283	$123.03	$123.05	$123.00
Purchase #5	$14.68	5.851%	$15.5389	$15.54	$15.55	$15.50
Purchase #6	$116.33	6.290%	$123.6472	$123.65	$123.65	$123.60
Purchase #7	$34.83	4.742%	$36.4816	$36.48	$36.50	$36.50
7 purchase totals =	$536.93		$589.5710	$589.58	$589.65	$589.40