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	$131.60	8.343%	$142.5794	$142.58	$142.60	$142.60
Purchase #2	$215.79	13.318%	$244.5289	$244.53	$244.55	$244.50
Purchase #3	$93.71	4.340%	$97.777	$97.78	$97.80	$97.80
Purchase #4	$218.46	5.244%	$229.916	$229.92	$229.90	$229.90
Purchase #5	$82.26	8.557%	$89.299	$89.30	$89.30	$89.30
Purchase #6	$92.42	10.313%	$101.9513	$101.95	$101.95	$102.00
Purchase #7	$163.89	9.565%	$179.5661	$179.57	$179.55	$179.60
7 purchase totals =	$998.13		$1,085.6177	$1,085.63	$1,085.65	$1,085.70