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	$67.56	7.787%	$72.8209	$72.82	$72.80	$72.80
Purchase #2	$130.32	9.132%	$142.2208	$142.22	$142.20	$142.20
Purchase #3	$125.80	4.498%	$131.4585	$131.46	$131.45	$131.50
Purchase #4	$77.62	9.542%	$85.0265	$85.03	$85.05	$85.00
Purchase #5	$187.69	7.671%	$202.0877	$202.09	$202.10	$202.10
Purchase #6	$82.32	3.481%	$85.1856	$85.19	$85.20	$85.20
Purchase #7	$90.38	13.736%	$102.7946	$102.79	$102.80	$102.80
7 purchase totals =	$761.69		$821.5946	$821.60	$821.60	$821.60