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	$109.47	3.818%	$113.6496	$113.65	$113.65	$113.60
Purchase #2	$102.87	9.356%	$112.4945	$112.49	$112.50	$112.50
Purchase #3	$111.88	7.495%	$120.2654	$120.27	$120.25	$120.30
Purchase #4	$159.63	13.835%	$181.7148	$181.71	$181.70	$181.70
Purchase #5	$83.63	10.870%	$92.7206	$92.72	$92.70	$92.70
Purchase #6	$11.25	4.832%	$11.7936	$11.79	$11.80	$11.80
Purchase #7	$165.83	11.719%	$185.2636	$185.26	$185.25	$185.30
7 purchase totals =	$744.56		$817.9021	$817.89	$817.85	$817.90