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	$114.94	10.149%	$126.6053	$126.61	$126.60	$126.60
Purchase #2	$73.50	12.770%	$82.886	$82.89	$82.90	$82.90
Purchase #3	$138.44	12.865%	$156.2503	$156.25	$156.25	$156.30
Purchase #4	$249.41	10.493%	$275.5806	$275.58	$275.60	$275.60
Purchase #5	$52.42	13.182%	$59.33	$59.33	$59.35	$59.30
Purchase #6	$92.69	4.342%	$96.7146	$96.71	$96.70	$96.70
Purchase #7	$10.87	4.796%	$11.3913	$11.39	$11.40	$11.40
7 purchase totals =	$732.27		$808.7581	$808.76	$808.80	$808.80