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	$52.73	7.765%	$56.8245	$56.82	$56.80	$56.80
Purchase #2	$18.86	10.139%	$20.7722	$20.77	$20.75	$20.80
Purchase #3	$105.46	6.728%	$112.5553	$112.56	$112.55	$112.60
Purchase #4	$220.44	7.694%	$237.4007	$237.40	$237.40	$237.40
Purchase #5	$164.85	12.501%	$185.4579	$185.46	$185.45	$185.50
Purchase #6	$191.97	12.466%	$215.901	$215.90	$215.90	$215.90
Purchase #7	$245.58	9.790%	$269.6223	$269.62	$269.60	$269.60
7 purchase totals =	$999.89		$1,098.5339	$1,098.53	$1,098.45	$1,098.60