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	$76.36	8.319%	$82.7124	$82.71	$82.70	$82.70
Purchase #2	$79.71	3.570%	$82.5556	$82.56	$82.55	$82.60
Purchase #3	$190.40	13.351%	$215.8203	$215.82	$215.80	$215.80
Purchase #4	$149.95	13.535%	$170.2457	$170.25	$170.25	$170.20
Purchase #5	$163.42	4.130%	$170.1692	$170.17	$170.15	$170.20
Purchase #6	$123.61	13.730%	$140.5817	$140.58	$140.60	$140.60
Purchase #7	$180.88	10.662%	$200.1654	$200.17	$200.15	$200.20
7 purchase totals =	$964.33		$1,062.2503	$1,062.26	$1,062.20	$1,062.30