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	$155.46	4.724%	$162.8039	$162.80	$162.80	$162.80
Purchase #2	$113.62	4.323%	$118.5318	$118.53	$118.55	$118.50
Purchase #3	$185.64	6.656%	$197.9962	$198.00	$198.00	$198.00
Purchase #4	$79.45	4.493%	$83.0197	$83.02	$83.00	$83.00
Purchase #5	$121.32	5.410%	$127.8834	$127.88	$127.90	$127.90
Purchase #6	$88.72	13.316%	$100.534	$100.53	$100.55	$100.50
Purchase #7	$208.27	5.333%	$219.377	$219.38	$219.40	$219.40
7 purchase totals =	$952.48		$1,010.1460	$1,010.14	$1,010.20	$1,010.10