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	$203.73	10.654%	$225.4354	$225.44	$225.45	$225.40
Purchase #2	$65.82	13.233%	$74.53	$74.53	$74.55	$74.50
Purchase #3	$152.97	3.428%	$158.2138	$158.21	$158.20	$158.20
Purchase #4	$23.77	7.375%	$25.523	$25.52	$25.50	$25.50
Purchase #5	$172.45	9.360%	$188.5913	$188.59	$188.60	$188.60
Purchase #6	$162.86	10.741%	$180.3528	$180.35	$180.35	$180.40
Purchase #7	$248.26	10.688%	$274.794	$274.79	$274.80	$274.80
7 purchase totals =	$1,029.86		$1,127.4403	$1,127.43	$1,127.45	$1,127.40