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	$62.41	4.798%	$65.4044	$65.40	$65.40	$65.40
Purchase #2	$225.44	10.831%	$249.8574	$249.86	$249.85	$249.90
Purchase #3	$99.30	4.683%	$103.9502	$103.95	$103.95	$104.00
Purchase #4	$190.28	3.363%	$196.6791	$196.68	$196.70	$196.70
Purchase #5	$245.41	8.393%	$266.0073	$266.01	$266.00	$266.00
Purchase #6	$136.55	6.582%	$145.5377	$145.54	$145.55	$145.50
Purchase #7	$82.50	7.136%	$88.3872	$88.39	$88.40	$88.40
7 purchase totals =	$1,041.89		$1,115.8233	$1,115.83	$1,115.85	$1,115.90