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	$29.58	7.617%	$31.8331	$31.83	$31.85	$31.80
Purchase #2	$161.25	12.644%	$181.6385	$181.64	$181.65	$181.60
Purchase #3	$173.75	8.643%	$188.7672	$188.77	$188.75	$188.80
Purchase #4	$246.72	3.378%	$255.0542	$255.05	$255.05	$255.10
Purchase #5	$118.75	7.226%	$127.3309	$127.33	$127.35	$127.30
Purchase #6	$164.34	12.710%	$185.2276	$185.23	$185.25	$185.20
Purchase #7	$215.92	7.134%	$231.3237	$231.32	$231.30	$231.30
7 purchase totals =	$1,110.31		$1,201.1752	$1,201.17	$1,201.20	$1,201.10