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	$128.86	12.531%	$145.0074	$145.01	$145.00	$145.00
Purchase #2	$64.57	12.351%	$72.545	$72.55	$72.55	$72.50
Purchase #3	$51.60	12.686%	$58.146	$58.15	$58.15	$58.10
Purchase #4	$93.98	10.494%	$103.8423	$103.84	$103.85	$103.80
Purchase #5	$131.63	5.742%	$139.1882	$139.19	$139.20	$139.20
Purchase #6	$138.42	12.802%	$156.1405	$156.14	$156.15	$156.10
Purchase #7	$29.31	9.430%	$32.0739	$32.07	$32.05	$32.10
7 purchase totals =	$638.37		$706.9433	$706.95	$706.95	$706.80