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	$98.66	7.281%	$105.8434	$105.84	$105.85	$105.80
Purchase #2	$29.41	7.440%	$31.5981	$31.60	$31.60	$31.60
Purchase #3	$169.83	11.862%	$189.9752	$189.98	$190.00	$190.00
Purchase #4	$208.55	3.479%	$215.8055	$215.81	$215.80	$215.80
Purchase #5	$103.43	12.771%	$116.639	$116.64	$116.65	$116.60
Purchase #6	$123.31	6.829%	$131.7308	$131.73	$131.75	$131.70
Purchase #7	$150.71	13.640%	$171.2668	$171.27	$171.25	$171.30
7 purchase totals =	$883.90		$962.8588	$962.87	$962.90	$962.80