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	$167.71	5.638%	$177.1655	$177.17	$177.15	$177.20
Purchase #2	$91.35	12.523%	$102.7898	$102.79	$102.80	$102.80
Purchase #3	$209.32	10.807%	$231.9412	$231.94	$231.95	$231.90
Purchase #4	$45.73	4.786%	$47.9186	$47.92	$47.90	$47.90
Purchase #5	$129.79	7.732%	$139.8254	$139.83	$139.85	$139.80
Purchase #6	$123.41	6.642%	$131.6069	$131.61	$131.60	$131.60
Purchase #7	$232.86	13.163%	$263.5114	$263.51	$263.50	$263.50
7 purchase totals =	$1,000.17		$1,094.7588	$1,094.77	$1,094.75	$1,094.70