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	$193.56	7.115%	$207.3318	$207.33	$207.35	$207.30
Purchase #2	$62.72	8.188%	$67.8555	$67.86	$67.85	$67.90
Purchase #3	$126.40	3.684%	$131.0566	$131.06	$131.05	$131.10
Purchase #4	$139.66	12.164%	$156.6482	$156.65	$156.65	$156.60
Purchase #5	$156.54	10.570%	$173.0863	$173.09	$173.10	$173.10
Purchase #6	$130.59	8.717%	$141.9735	$141.97	$141.95	$142.00
Purchase #7	$219.46	5.398%	$231.3065	$231.31	$231.30	$231.30
7 purchase totals =	$1,028.93		$1,109.2584	$1,109.27	$1,109.25	$1,109.30