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	$186.64	5.551%	$197.0004	$197.00	$197.00	$197.00
Purchase #2	$54.80	5.331%	$57.7214	$57.72	$57.70	$57.70
Purchase #3	$249.48	13.224%	$282.4712	$282.47	$282.45	$282.50
Purchase #4	$225.37	13.732%	$256.3178	$256.32	$256.30	$256.30
Purchase #5	$152.57	10.275%	$168.2466	$168.25	$168.25	$168.20
Purchase #6	$134.76	6.622%	$143.6838	$143.68	$143.70	$143.70
Purchase #7	$43.25	5.198%	$45.4981	$45.50	$45.50	$45.50
7 purchase totals =	$1,046.87		$1,150.9393	$1,150.94	$1,150.90	$1,150.90