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	$160.73	6.518%	$171.2064	$171.21	$171.20	$171.20
Purchase #2	$5.54	3.230%	$5.7189	$5.72	$5.70	$5.70
Purchase #3	$208.68	5.213%	$219.5585	$219.56	$219.55	$219.60
Purchase #4	$173.85	3.722%	$180.3207	$180.32	$180.30	$180.30
Purchase #5	$183.83	4.189%	$191.5306	$191.53	$191.55	$191.50
Purchase #6	$237.37	12.217%	$266.3695	$266.37	$266.35	$266.40
Purchase #7	$189.80	3.715%	$196.8511	$196.85	$196.85	$196.90
7 purchase totals =	$1,159.80		$1,231.5557	$1,231.56	$1,231.50	$1,231.60