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	$116.86	12.161%	$131.0713	$131.07	$131.05	$131.10
Purchase #2	$135.56	12.308%	$152.2447	$152.24	$152.25	$152.20
Purchase #3	$187.44	8.805%	$203.9441	$203.94	$203.95	$203.90
Purchase #4	$184.83	7.364%	$198.4409	$198.44	$198.45	$198.40
Purchase #5	$250.82	6.237%	$266.4636	$266.46	$266.45	$266.50
Purchase #6	$46.73	10.440%	$51.6086	$51.61	$51.60	$51.60
Purchase #7	$51.52	9.323%	$56.3232	$56.32	$56.30	$56.30
7 purchase totals =	$973.76		$1,060.0964	$1,060.08	$1,060.05	$1,060.00