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	$240.88	5.637%	$254.4584	$254.46	$254.45	$254.50
Purchase #2	$41.61	4.293%	$43.3963	$43.40	$43.40	$43.40
Purchase #3	$168.40	10.358%	$185.8429	$185.84	$185.85	$185.80
Purchase #4	$173.89	8.165%	$188.0881	$188.09	$188.10	$188.10
Purchase #5	$86.30	12.311%	$96.9244	$96.92	$96.90	$96.90
Purchase #6	$46.94	12.577%	$52.8436	$52.84	$52.85	$52.80
Purchase #7	$167.69	7.458%	$180.1963	$180.20	$180.20	$180.20
7 purchase totals =	$925.71		$1,001.7500	$1,001.75	$1,001.75	$1,001.70