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	$250.86	12.569%	$282.3906	$282.39	$282.40	$282.40
Purchase #2	$107.46	4.170%	$111.9411	$111.94	$111.95	$111.90
Purchase #3	$25.51	8.174%	$27.5952	$27.60	$27.60	$27.60
Purchase #4	$76.38	6.382%	$81.2546	$81.25	$81.25	$81.30
Purchase #5	$85.94	13.702%	$97.7155	$97.72	$97.70	$97.70
Purchase #6	$178.70	9.705%	$196.0428	$196.04	$196.05	$196.00
Purchase #7	$217.77	7.617%	$234.3575	$234.36	$234.35	$234.40
7 purchase totals =	$942.62		$1,031.2973	$1,031.30	$1,031.30	$1,031.30