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	$82.41	11.728%	$92.075	$92.08	$92.10	$92.10
Purchase #2	$165.80	7.638%	$178.4638	$178.46	$178.45	$178.50
Purchase #3	$104.57	7.583%	$112.4995	$112.50	$112.50	$112.50
Purchase #4	$210.79	9.367%	$230.5347	$230.53	$230.55	$230.50
Purchase #5	$227.85	5.540%	$240.4729	$240.47	$240.45	$240.50
Purchase #6	$103.59	10.140%	$114.094	$114.09	$114.10	$114.10
Purchase #7	$139.45	3.334%	$144.0993	$144.10	$144.10	$144.10
7 purchase totals =	$1,034.46		$1,112.2392	$1,112.23	$1,112.25	$1,112.30