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	$180.57	4.862%	$189.3493	$189.35	$189.35	$189.30
Purchase #2	$123.48	7.712%	$133.0028	$133.00	$133.00	$133.00
Purchase #3	$179.54	3.102%	$185.1093	$185.11	$185.10	$185.10
Purchase #4	$60.52	8.148%	$65.4512	$65.45	$65.45	$65.50
Purchase #5	$248.95	6.641%	$265.4828	$265.48	$265.50	$265.50
Purchase #6	$54.99	3.678%	$57.0125	$57.01	$57.00	$57.00
Purchase #7	$167.52	7.608%	$180.2649	$180.26	$180.25	$180.30
7 purchase totals =	$1,015.57		$1,075.6728	$1,075.66	$1,075.65	$1,075.70