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	$186.82	9.239%	$204.0803	$204.08	$204.10	$204.10
Purchase #2	$188.79	7.588%	$203.1154	$203.12	$203.10	$203.10
Purchase #3	$40.27	7.475%	$43.2802	$43.28	$43.30	$43.30
Purchase #4	$144.86	8.287%	$156.8645	$156.86	$156.85	$156.90
Purchase #5	$51.89	9.185%	$56.6561	$56.66	$56.65	$56.70
Purchase #6	$199.63	4.583%	$208.779	$208.78	$208.80	$208.80
Purchase #7	$59.57	13.502%	$67.6131	$67.61	$67.60	$67.60
7 purchase totals =	$871.83		$940.3886	$940.39	$940.40	$940.50