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	$161.77	4.144%	$168.4737	$168.47	$168.45	$168.50
Purchase #2	$17.53	7.344%	$18.8174	$18.82	$18.80	$18.80
Purchase #3	$136.45	10.605%	$150.9205	$150.92	$150.90	$150.90
Purchase #4	$220.59	11.269%	$245.4483	$245.45	$245.45	$245.40
Purchase #5	$25.27	12.457%	$28.4179	$28.42	$28.40	$28.40
Purchase #6	$40.94	5.384%	$43.1442	$43.14	$43.15	$43.10
Purchase #7	$242.44	11.661%	$270.7109	$270.71	$270.70	$270.70
7 purchase totals =	$844.99		$925.9329	$925.93	$925.85	$925.80