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	$59.45	10.289%	$65.5668	$65.57	$65.55	$65.60
Purchase #2	$246.38	9.852%	$270.6534	$270.65	$270.65	$270.70
Purchase #3	$17.75	4.793%	$18.6008	$18.60	$18.60	$18.60
Purchase #4	$210.61	3.179%	$217.3053	$217.31	$217.30	$217.30
Purchase #5	$209.70	12.765%	$236.4682	$236.47	$236.45	$236.50
Purchase #6	$47.34	6.632%	$50.4796	$50.48	$50.50	$50.50
Purchase #7	$133.88	12.641%	$150.8038	$150.80	$150.80	$150.80
7 purchase totals =	$925.11		$1,009.8779	$1,009.88	$1,009.85	$1,010.00