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	$129.96	5.108%	$136.5984	$136.60	$136.60	$136.60
Purchase #2	$83.61	3.496%	$86.533	$86.53	$86.55	$86.50
Purchase #3	$68.87	8.170%	$74.4967	$74.50	$74.50	$74.50
Purchase #4	$115.84	6.574%	$123.4553	$123.46	$123.45	$123.50
Purchase #5	$169.55	3.478%	$175.4469	$175.45	$175.45	$175.40
Purchase #6	$241.60	10.437%	$266.8158	$266.82	$266.80	$266.80
Purchase #7	$178.33	7.379%	$191.489	$191.49	$191.50	$191.50
7 purchase totals =	$987.76		$1,054.8351	$1,054.85	$1,054.85	$1,054.80