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	$59.86	12.660%	$67.4383	$67.44	$67.45	$67.40
Purchase #2	$240.97	10.316%	$265.8285	$265.83	$265.85	$265.80
Purchase #3	$90.65	12.719%	$102.1798	$102.18	$102.20	$102.20
Purchase #4	$179.35	9.522%	$196.4277	$196.43	$196.45	$196.40
Purchase #5	$186.74	12.279%	$209.6698	$209.67	$209.65	$209.70
Purchase #6	$51.80	10.230%	$57.0991	$57.10	$57.10	$57.10
Purchase #7	$114.82	10.746%	$127.1586	$127.16	$127.15	$127.20
7 purchase totals =	$924.19		$1,025.8018	$1,025.81	$1,025.85	$1,025.80