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	$124.57	12.857%	$140.586	$140.59	$140.60	$140.60
Purchase #2	$112.48	3.404%	$116.3088	$116.31	$116.30	$116.30
Purchase #3	$217.80	12.144%	$244.2496	$244.25	$244.25	$244.20
Purchase #4	$136.32	4.423%	$142.3494	$142.35	$142.35	$142.30
Purchase #5	$181.41	9.432%	$198.5206	$198.52	$198.50	$198.50
Purchase #6	$109.48	11.217%	$121.7604	$121.76	$121.75	$121.80
Purchase #7	$98.92	4.383%	$103.2557	$103.26	$103.25	$103.30
7 purchase totals =	$980.98		$1,067.0305	$1,067.04	$1,067.00	$1,067.00