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	$89.87	12.439%	$101.0489	$101.05	$101.05	$101.00
Purchase #2	$174.83	13.542%	$198.5055	$198.51	$198.50	$198.50
Purchase #3	$52.48	13.514%	$59.5721	$59.57	$59.55	$59.60
Purchase #4	$224.65	13.674%	$255.3686	$255.37	$255.35	$255.40
Purchase #5	$63.32	10.505%	$69.9718	$69.97	$69.95	$70.00
Purchase #6	$234.81	4.503%	$245.3835	$245.38	$245.40	$245.40
Purchase #7	$73.29	11.264%	$81.5454	$81.55	$81.55	$81.50
7 purchase totals =	$913.25		$1,011.3958	$1,011.40	$1,011.35	$1,011.40