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	$54.27	10.289%	$59.8538	$59.85	$59.85	$59.90
Purchase #2	$163.63	9.446%	$179.0865	$179.09	$179.10	$179.10
Purchase #3	$170.27	3.561%	$176.3333	$176.33	$176.35	$176.30
Purchase #4	$240.86	7.229%	$258.2718	$258.27	$258.25	$258.30
Purchase #5	$91.63	5.627%	$96.786	$96.79	$96.80	$96.80
Purchase #6	$64.79	7.683%	$69.7678	$69.77	$69.75	$69.80
Purchase #7	$225.55	13.502%	$256.0038	$256.00	$256.00	$256.00
7 purchase totals =	$1,011.00		$1,096.1030	$1,096.10	$1,096.10	$1,096.20