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	$72.89	3.707%	$75.592	$75.59	$75.60	$75.60
Purchase #2	$231.71	10.116%	$255.1498	$255.15	$255.15	$255.10
Purchase #3	$200.78	12.300%	$225.4759	$225.48	$225.50	$225.50
Purchase #4	$211.27	13.174%	$239.1027	$239.10	$239.10	$239.10
Purchase #5	$231.31	4.789%	$242.3874	$242.39	$242.40	$242.40
Purchase #6	$234.90	12.660%	$264.6383	$264.64	$264.65	$264.60
Purchase #7	$41.52	5.666%	$43.8725	$43.87	$43.85	$43.90
7 purchase totals =	$1,224.38		$1,346.2186	$1,346.22	$1,346.25	$1,346.20