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	$182.40	5.478%	$192.3919	$192.39	$192.40	$192.40
Purchase #2	$161.41	6.731%	$172.2745	$172.27	$172.25	$172.30
Purchase #3	$178.91	3.768%	$185.6513	$185.65	$185.65	$185.70
Purchase #4	$237.25	13.430%	$269.1127	$269.11	$269.10	$269.10
Purchase #5	$217.69	3.340%	$224.9608	$224.96	$224.95	$225.00
Purchase #6	$78.65	9.226%	$85.9062	$85.91	$85.90	$85.90
Purchase #7	$162.43	6.591%	$173.1358	$173.14	$173.15	$173.10
7 purchase totals =	$1,218.74		$1,303.4332	$1,303.43	$1,303.40	$1,303.50