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	$176.39	8.664%	$191.6724	$191.67	$191.65	$191.70
Purchase #2	$111.55	4.770%	$116.8709	$116.87	$116.85	$116.90
Purchase #3	$132.76	4.598%	$138.8643	$138.86	$138.85	$138.90
Purchase #4	$150.97	11.830%	$168.8298	$168.83	$168.85	$168.80
Purchase #5	$186.25	7.742%	$200.6695	$200.67	$200.65	$200.70
Purchase #6	$45.40	11.731%	$50.7259	$50.73	$50.75	$50.70
Purchase #7	$191.63	12.231%	$215.0683	$215.07	$215.05	$215.10
7 purchase totals =	$994.95		$1,082.7011	$1,082.70	$1,082.65	$1,082.80