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	$151.55	9.768%	$166.3534	$166.35	$166.35	$166.40
Purchase #2	$180.35	5.407%	$190.1015	$190.10	$190.10	$190.10
Purchase #3	$104.44	10.772%	$115.6903	$115.69	$115.70	$115.70
Purchase #4	$76.31	8.464%	$82.7689	$82.77	$82.75	$82.80
Purchase #5	$241.89	13.234%	$273.9017	$273.90	$273.90	$273.90
Purchase #6	$198.48	3.459%	$205.3454	$205.35	$205.35	$205.30
Purchase #7	$108.72	13.427%	$123.3178	$123.32	$123.30	$123.30
7 purchase totals =	$1,061.74		$1,157.4790	$1,157.48	$1,157.45	$1,157.50