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	$210.50	3.329%	$217.5075	$217.51	$217.50	$217.50
Purchase #2	$86.65	8.809%	$94.283	$94.28	$94.30	$94.30
Purchase #3	$108.87	3.680%	$112.8764	$112.88	$112.90	$112.90
Purchase #4	$144.69	8.457%	$156.9264	$156.93	$156.95	$156.90
Purchase #5	$140.82	4.441%	$147.0738	$147.07	$147.05	$147.10
Purchase #6	$148.41	3.670%	$153.8566	$153.86	$153.85	$153.90
Purchase #7	$148.43	13.273%	$168.1311	$168.13	$168.15	$168.10
7 purchase totals =	$988.37		$1,050.6548	$1,050.66	$1,050.70	$1,050.70