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	$200.34	13.442%	$227.2697	$227.27	$227.25	$227.30
Purchase #2	$103.41	8.454%	$112.1523	$112.15	$112.15	$112.20
Purchase #3	$62.44	7.368%	$67.0406	$67.04	$67.05	$67.00
Purchase #4	$189.46	5.731%	$200.318	$200.32	$200.30	$200.30
Purchase #5	$39.79	10.170%	$43.8366	$43.84	$43.85	$43.80
Purchase #6	$234.40	9.313%	$256.2297	$256.23	$256.25	$256.20
Purchase #7	$134.94	7.135%	$144.568	$144.57	$144.55	$144.60
7 purchase totals =	$964.78		$1,051.4149	$1,051.42	$1,051.40	$1,051.40