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	$195.59	12.755%	$220.5375	$220.54	$220.55	$220.50
Purchase #2	$29.80	12.584%	$33.55	$33.55	$33.55	$33.60
Purchase #3	$150.84	13.806%	$171.665	$171.67	$171.65	$171.70
Purchase #4	$158.38	10.272%	$174.6488	$174.65	$174.65	$174.60
Purchase #5	$53.82	4.626%	$56.3097	$56.31	$56.30	$56.30
Purchase #6	$100.94	13.415%	$114.4811	$114.48	$114.50	$114.50
Purchase #7	$244.42	6.585%	$260.5151	$260.52	$260.50	$260.50
7 purchase totals =	$933.79		$1,031.7072	$1,031.72	$1,031.70	$1,031.70