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	$208.62	3.348%	$215.6046	$215.60	$215.60	$215.60
Purchase #2	$164.50	3.850%	$170.8333	$170.83	$170.85	$170.80
Purchase #3	$47.98	12.556%	$54.0044	$54.00	$54.00	$54.00
Purchase #4	$35.89	7.439%	$38.5599	$38.56	$38.55	$38.60
Purchase #5	$210.35	5.292%	$221.4817	$221.48	$221.50	$221.50
Purchase #6	$53.95	13.711%	$61.3471	$61.35	$61.35	$61.30
Purchase #7	$212.80	12.643%	$239.7043	$239.70	$239.70	$239.70
7 purchase totals =	$934.09		$1,001.5353	$1,001.52	$1,001.55	$1,001.50