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	$33.63	7.866%	$36.2753	$36.28	$36.30	$36.30
Purchase #2	$208.99	12.585%	$235.2914	$235.29	$235.30	$235.30
Purchase #3	$120.28	6.319%	$127.8805	$127.88	$127.90	$127.90
Purchase #4	$43.33	5.824%	$45.8535	$45.85	$45.85	$45.90
Purchase #5	$199.67	4.362%	$208.3796	$208.38	$208.40	$208.40
Purchase #6	$150.53	11.223%	$167.424	$167.42	$167.40	$167.40
Purchase #7	$202.54	9.857%	$222.5044	$222.50	$222.50	$222.50
7 purchase totals =	$958.97		$1,043.6087	$1,043.60	$1,043.65	$1,043.70