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	$31.87	5.418%	$33.5967	$33.60	$33.60	$33.60
Purchase #2	$215.39	13.750%	$245.0061	$245.01	$245.00	$245.00
Purchase #3	$225.59	7.608%	$242.7529	$242.75	$242.75	$242.80
Purchase #4	$86.78	4.297%	$90.5089	$90.51	$90.50	$90.50
Purchase #5	$117.63	11.356%	$130.9881	$130.99	$131.00	$131.00
Purchase #6	$153.31	3.272%	$158.3263	$158.33	$158.35	$158.30
Purchase #7	$158.68	5.156%	$166.8615	$166.86	$166.85	$166.90
7 purchase totals =	$989.25		$1,068.0405	$1,068.05	$1,068.05	$1,068.10