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	$97.48	8.122%	$105.3973	$105.40	$105.40	$105.40
Purchase #2	$123.63	5.570%	$130.5162	$130.52	$130.50	$130.50
Purchase #3	$127.81	11.519%	$142.5324	$142.53	$142.55	$142.50
Purchase #4	$169.47	4.819%	$177.6368	$177.64	$177.65	$177.60
Purchase #5	$217.53	6.438%	$231.5346	$231.53	$231.55	$231.50
Purchase #6	$148.25	9.656%	$162.565	$162.57	$162.55	$162.60
Purchase #7	$76.36	5.802%	$80.7904	$80.79	$80.80	$80.80
7 purchase totals =	$960.53		$1,030.9727	$1,030.98	$1,031.00	$1,030.90