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	$243.29	5.238%	$256.0335	$256.03	$256.05	$256.00
Purchase #2	$226.40	7.572%	$243.543	$243.54	$243.55	$243.50
Purchase #3	$187.69	12.128%	$210.453	$210.45	$210.45	$210.50
Purchase #4	$198.28	12.786%	$223.6321	$223.63	$223.65	$223.60
Purchase #5	$245.39	11.785%	$274.3092	$274.31	$274.30	$274.30
Purchase #6	$72.43	13.146%	$81.9516	$81.95	$81.95	$82.00
Purchase #7	$11.42	9.859%	$12.5459	$12.55	$12.55	$12.50
7 purchase totals =	$1,184.90		$1,302.4683	$1,302.46	$1,302.50	$1,302.40