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	$171.73	11.187%	$190.9414	$190.94	$190.95	$190.90
Purchase #2	$171.88	11.510%	$191.6634	$191.66	$191.65	$191.70
Purchase #3	$163.76	9.659%	$179.5776	$179.58	$179.60	$179.60
Purchase #4	$64.44	4.703%	$67.4706	$67.47	$67.45	$67.50
Purchase #5	$180.75	7.731%	$194.7238	$194.72	$194.70	$194.70
Purchase #6	$12.40	5.383%	$13.0675	$13.07	$13.05	$13.10
Purchase #7	$151.62	8.172%	$164.0104	$164.01	$164.00	$164.00
7 purchase totals =	$916.58		$1,001.4547	$1,001.45	$1,001.40	$1,001.50