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	$127.65	10.158%	$140.6167	$140.62	$140.60	$140.60
Purchase #2	$53.97	10.746%	$59.7696	$59.77	$59.75	$59.80
Purchase #3	$8.46	4.224%	$8.8174	$8.82	$8.80	$8.80
Purchase #4	$242.80	6.577%	$258.769	$258.77	$258.75	$258.80
Purchase #5	$245.36	9.865%	$269.5648	$269.56	$269.55	$269.60
Purchase #6	$72.53	8.337%	$78.5768	$78.58	$78.60	$78.60
Purchase #7	$247.52	6.305%	$263.1261	$263.13	$263.15	$263.10
7 purchase totals =	$998.29		$1,079.2404	$1,079.25	$1,079.20	$1,079.30