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	$81.32	4.610%	$85.0689	$85.07	$85.05	$85.10
Purchase #2	$114.80	7.354%	$123.2424	$123.24	$123.25	$123.20
Purchase #3	$144.81	4.589%	$151.4553	$151.46	$151.45	$151.50
Purchase #4	$171.82	6.191%	$182.4574	$182.46	$182.45	$182.50
Purchase #5	$96.85	6.210%	$102.8644	$102.86	$102.85	$102.90
Purchase #6	$210.70	13.797%	$239.7703	$239.77	$239.75	$239.80
Purchase #7	$157.86	5.362%	$166.3245	$166.32	$166.30	$166.30
7 purchase totals =	$978.16		$1,051.1832	$1,051.18	$1,051.10	$1,051.30