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	$119.60	7.735%	$128.8511	$128.85	$128.85	$128.90
Purchase #2	$149.98	8.371%	$162.5348	$162.53	$162.55	$162.50
Purchase #3	$155.73	10.695%	$172.3853	$172.39	$172.40	$172.40
Purchase #4	$153.37	3.235%	$158.3315	$158.33	$158.35	$158.30
Purchase #5	$27.26	6.259%	$28.9662	$28.97	$28.95	$29.00
Purchase #6	$77.84	11.699%	$86.9465	$86.95	$86.95	$86.90
Purchase #7	$248.44	13.853%	$282.8564	$282.86	$282.85	$282.90
7 purchase totals =	$932.22		$1,020.8718	$1,020.88	$1,020.90	$1,020.90