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	$180.94	8.433%	$196.1987	$196.20	$196.20	$196.20
Purchase #2	$47.39	8.406%	$51.3736	$51.37	$51.35	$51.40
Purchase #3	$175.77	5.303%	$185.0911	$185.09	$185.10	$185.10
Purchase #4	$14.61	13.674%	$16.6078	$16.61	$16.60	$16.60
Purchase #5	$202.46	10.146%	$223.0016	$223.00	$223.00	$223.00
Purchase #6	$185.46	12.648%	$208.917	$208.92	$208.90	$208.90
Purchase #7	$227.68	12.619%	$256.4109	$256.41	$256.40	$256.40
7 purchase totals =	$1,034.31		$1,137.6007	$1,137.60	$1,137.55	$1,137.60