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	$217.55	11.757%	$243.1274	$243.13	$243.15	$243.10
Purchase #2	$202.83	13.623%	$230.4615	$230.46	$230.45	$230.50
Purchase #3	$177.69	4.522%	$185.7251	$185.73	$185.75	$185.70
Purchase #4	$168.34	9.356%	$184.0899	$184.09	$184.10	$184.10
Purchase #5	$109.60	12.327%	$123.1104	$123.11	$123.10	$123.10
Purchase #6	$220.75	9.415%	$241.5336	$241.53	$241.55	$241.50
Purchase #7	$193.95	12.567%	$218.3237	$218.32	$218.30	$218.30
7 purchase totals =	$1,290.71		$1,426.3716	$1,426.37	$1,426.40	$1,426.30