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	$230.81	13.441%	$261.8332	$261.83	$261.85	$261.80
Purchase #2	$96.85	13.384%	$109.8124	$109.81	$109.80	$109.80
Purchase #3	$183.89	13.609%	$208.9156	$208.92	$208.90	$208.90
Purchase #4	$80.85	3.265%	$83.4898	$83.49	$83.50	$83.50
Purchase #5	$56.98	4.668%	$59.6398	$59.64	$59.65	$59.60
Purchase #6	$91.63	10.645%	$101.384	$101.38	$101.40	$101.40
Purchase #7	$208.39	4.802%	$218.3969	$218.40	$218.40	$218.40
7 purchase totals =	$949.40		$1,043.4717	$1,043.47	$1,043.50	$1,043.40