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	$186.72	7.116%	$200.007	$200.01	$200.00	$200.00
Purchase #2	$130.30	13.649%	$148.0846	$148.08	$148.10	$148.10
Purchase #3	$67.54	6.754%	$72.1017	$72.10	$72.10	$72.10
Purchase #4	$51.34	5.791%	$54.3131	$54.31	$54.30	$54.30
Purchase #5	$93.44	3.292%	$96.516	$96.52	$96.50	$96.50
Purchase #6	$51.56	4.666%	$53.9658	$53.97	$53.95	$54.00
Purchase #7	$112.82	3.189%	$116.4178	$116.42	$116.40	$116.40
7 purchase totals =	$693.72		$741.4060	$741.41	$741.35	$741.40