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	$50.80	9.864%	$55.8109	$55.81	$55.80	$55.80
Purchase #2	$187.94	4.462%	$196.3259	$196.33	$196.35	$196.30
Purchase #3	$102.97	10.225%	$113.4987	$113.50	$113.50	$113.50
Purchase #4	$245.40	4.731%	$257.0099	$257.01	$257.00	$257.00
Purchase #5	$166.53	12.321%	$187.0482	$187.05	$187.05	$187.00
Purchase #6	$231.36	5.297%	$243.6151	$243.62	$243.60	$243.60
Purchase #7	$37.30	13.583%	$42.3665	$42.37	$42.35	$42.40
7 purchase totals =	$1,022.30		$1,095.6752	$1,095.69	$1,095.65	$1,095.60