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	$196.57	11.365%	$218.9102	$218.91	$218.90	$218.90
Purchase #2	$150.54	7.765%	$162.2294	$162.23	$162.25	$162.20
Purchase #3	$120.69	4.703%	$126.3661	$126.37	$126.35	$126.40
Purchase #4	$51.68	9.198%	$56.4335	$56.43	$56.45	$56.40
Purchase #5	$41.40	13.803%	$47.1144	$47.11	$47.10	$47.10
Purchase #6	$147.55	6.332%	$156.8929	$156.89	$156.90	$156.90
Purchase #7	$246.89	6.566%	$263.1008	$263.10	$263.10	$263.10
7 purchase totals =	$955.32		$1,031.0473	$1,031.04	$1,031.05	$1,031.00