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	$202.71	9.693%	$222.3587	$222.36	$222.35	$222.40
Purchase #2	$118.90	13.494%	$134.9444	$134.94	$134.95	$134.90
Purchase #3	$200.41	8.443%	$217.3306	$217.33	$217.35	$217.30
Purchase #4	$10.91	8.645%	$11.8532	$11.85	$11.85	$11.90
Purchase #5	$25.57	13.665%	$29.0641	$29.06	$29.05	$29.10
Purchase #6	$86.96	4.489%	$90.8636	$90.86	$90.85	$90.90
Purchase #7	$54.41	6.373%	$57.8775	$57.88	$57.90	$57.90
7 purchase totals =	$699.87		$764.2921	$764.28	$764.30	$764.40