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	$75.96	6.570%	$80.9506	$80.95	$80.95	$81.00
Purchase #2	$116.41	5.709%	$123.0558	$123.06	$123.05	$123.10
Purchase #3	$138.40	6.642%	$147.5925	$147.59	$147.60	$147.60
Purchase #4	$12.55	6.623%	$13.3812	$13.38	$13.40	$13.40
Purchase #5	$101.39	11.364%	$112.912	$112.91	$112.90	$112.90
Purchase #6	$168.50	6.403%	$179.2891	$179.29	$179.30	$179.30
Purchase #7	$39.99	6.715%	$42.6753	$42.68	$42.70	$42.70
7 purchase totals =	$653.20		$699.8565	$699.86	$699.90	$700.00