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	$189.33	4.702%	$198.2323	$198.23	$198.25	$198.20
Purchase #2	$167.95	3.417%	$173.6889	$173.69	$173.70	$173.70
Purchase #3	$105.57	7.787%	$113.7907	$113.79	$113.80	$113.80
Purchase #4	$71.94	8.832%	$78.2937	$78.29	$78.30	$78.30
Purchase #5	$232.59	7.713%	$250.5297	$250.53	$250.55	$250.50
Purchase #6	$109.47	3.160%	$112.9293	$112.93	$112.95	$112.90
Purchase #7	$208.60	9.425%	$228.2606	$228.26	$228.25	$228.30
7 purchase totals =	$1,085.45		$1,155.7252	$1,155.72	$1,155.80	$1,155.70