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	$192.38	4.388%	$200.8216	$200.82	$200.80	$200.80
Purchase #2	$78.93	5.802%	$83.5095	$83.51	$83.50	$83.50
Purchase #3	$233.63	8.399%	$253.2526	$253.25	$253.25	$253.30
Purchase #4	$89.70	13.263%	$101.5969	$101.60	$101.60	$101.60
Purchase #5	$103.44	9.174%	$112.9296	$112.93	$112.95	$112.90
Purchase #6	$76.64	8.545%	$83.1889	$83.19	$83.20	$83.20
Purchase #7	$39.47	6.441%	$42.0123	$42.01	$42.00	$42.00
7 purchase totals =	$814.19		$877.3114	$877.31	$877.30	$877.30