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	$162.69	13.333%	$184.3815	$184.38	$184.40	$184.40
Purchase #2	$81.87	6.872%	$87.4961	$87.50	$87.50	$87.50
Purchase #3	$71.25	10.121%	$78.4612	$78.46	$78.45	$78.50
Purchase #4	$208.69	3.601%	$216.2049	$216.20	$216.20	$216.20
Purchase #5	$97.60	13.807%	$111.0756	$111.08	$111.10	$111.10
Purchase #6	$202.56	10.354%	$223.5331	$223.53	$223.55	$223.50
Purchase #7	$13.36	5.715%	$14.1235	$14.12	$14.10	$14.10
7 purchase totals =	$838.02		$915.2759	$915.27	$915.30	$915.30