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	$231.34	4.155%	$240.9522	$240.95	$240.95	$241.00
Purchase #2	$81.91	4.768%	$85.8155	$85.82	$85.80	$85.80
Purchase #3	$249.90	8.700%	$271.6413	$271.64	$271.65	$271.60
Purchase #4	$136.93	11.706%	$152.959	$152.96	$152.95	$153.00
Purchase #5	$180.91	3.536%	$187.307	$187.31	$187.30	$187.30
Purchase #6	$145.81	11.333%	$162.3346	$162.33	$162.35	$162.30
Purchase #7	$196.53	13.509%	$223.0792	$223.08	$223.10	$223.10
7 purchase totals =	$1,223.33		$1,324.0888	$1,324.09	$1,324.10	$1,324.10