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	$163.65	9.645%	$179.434	$179.43	$179.45	$179.40
Purchase #2	$167.99	10.393%	$185.4492	$185.45	$185.45	$185.40
Purchase #3	$205.86	7.460%	$221.2172	$221.22	$221.20	$221.20
Purchase #4	$152.55	12.529%	$171.663	$171.66	$171.65	$171.70
Purchase #5	$31.80	8.333%	$34.4499	$34.45	$34.45	$34.40
Purchase #6	$35.56	4.735%	$37.2438	$37.24	$37.25	$37.20
Purchase #7	$95.36	9.501%	$104.4202	$104.42	$104.40	$104.40
7 purchase totals =	$852.77		$933.8773	$933.87	$933.85	$933.70