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	$234.78	10.674%	$259.8404	$259.84	$259.85	$259.80
Purchase #2	$53.82	10.737%	$59.5987	$59.60	$59.60	$59.60
Purchase #3	$51.41	9.813%	$56.4549	$56.45	$56.45	$56.50
Purchase #4	$54.93	5.441%	$57.9187	$57.92	$57.90	$57.90
Purchase #5	$200.28	5.874%	$212.0444	$212.04	$212.05	$212.00
Purchase #6	$237.48	5.270%	$249.9952	$250.00	$250.00	$250.00
Purchase #7	$211.53	3.300%	$218.5105	$218.51	$218.50	$218.50
7 purchase totals =	$1,044.23		$1,114.3628	$1,114.36	$1,114.35	$1,114.30