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	$31.88	13.639%	$36.2281	$36.23	$36.25	$36.20
Purchase #2	$103.31	13.566%	$117.325	$117.33	$117.35	$117.30
Purchase #3	$124.59	8.184%	$134.7864	$134.79	$134.80	$134.80
Purchase #4	$72.94	6.559%	$77.7241	$77.72	$77.70	$77.70
Purchase #5	$218.71	3.206%	$225.7218	$225.72	$225.70	$225.70
Purchase #6	$171.66	5.719%	$181.4772	$181.48	$181.50	$181.50
Purchase #7	$222.43	10.528%	$245.8474	$245.85	$245.85	$245.80
7 purchase totals =	$945.52		$1,019.1100	$1,019.12	$1,019.15	$1,019.00