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	$156.78	9.673%	$171.9453	$171.95	$171.95	$171.90
Purchase #2	$167.60	7.327%	$179.8801	$179.88	$179.90	$179.90
Purchase #3	$221.75	12.469%	$249.4	$249.40	$249.40	$249.40
Purchase #4	$35.47	8.806%	$38.5935	$38.59	$38.60	$38.60
Purchase #5	$201.96	6.397%	$214.8794	$214.88	$214.90	$214.90
Purchase #6	$84.95	6.291%	$90.2942	$90.29	$90.30	$90.30
Purchase #7	$53.26	8.833%	$57.9645	$57.96	$57.95	$58.00
7 purchase totals =	$921.77		$1,002.9570	$1,002.95	$1,003.00	$1,003.00