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	$239.71	7.481%	$257.6427	$257.64	$257.65	$257.60
Purchase #2	$200.40	6.698%	$213.8228	$213.82	$213.80	$213.80
Purchase #3	$164.39	6.191%	$174.5674	$174.57	$174.55	$174.60
Purchase #4	$106.79	11.746%	$119.3336	$119.33	$119.35	$119.30
Purchase #5	$112.93	13.166%	$127.7984	$127.80	$127.80	$127.80
Purchase #6	$169.77	4.850%	$178.0038	$178.00	$178.00	$178.00
Purchase #7	$67.39	7.197%	$72.2401	$72.24	$72.25	$72.20
7 purchase totals =	$1,061.38		$1,143.4088	$1,143.40	$1,143.40	$1,143.30